Astronomical vs. Fixed-Time Zmanim

וְאֵיזֶהוּ בֵּין הַשְּׁמָשׁוֹת? — מִשֶּׁתִּשְׁקַע הַחַמָּה כָּל זְמַן שֶׁפְּנֵי מִזְרָח מַאֲדִימִין. הִכְסִיף הַתַּחְתּוֹן וְלֹא הִכְסִיף הָעֶלְיוֹן — בֵּין הַשְּׁמָשׁוֹת. הִכְסִיף הָעֶלְיוֹן וְהִשְׁוָה לַתַּחְתּוֹן — זֶהוּ לַיְלָה, דִּבְרֵי רַבִּי יְהוּדָה. רַבִּי נְחֶמְיָה אוֹמֵר: כְּדֵי שֶׁיְּהַלֵּךְ אָדָם מִשֶּׁתִּשְׁקַע הַחַמָּה חֲצִי מִיל. רַבִּי יוֹסִי אוֹמֵר: בֵּין הַשְּׁמָשׁוֹת כְּהֶרֶף עַיִן, זֶה נִכְנָס וְזֶה יוֹצֵא, וְאִי אֶפְשָׁר לַעֲמוֹד עָלָיו. וְאָזְדוּ לְטַעְמַיְיהוּ, דְּאִיתְּמַר: שִׁיעוּר בֵּין הַשְּׁמָשׁוֹת בְּכַמָּה? אָמַר רַבָּה אָמַר רַב יְהוּדָה אָמַר שְׁמוּאֵל: שְׁלֹשָׁה חֶלְקֵי מִיל. מַאי שְׁלֹשָׁה חֶלְקֵי מִיל? אִילֵימָא תְּלָתָא פַּלְגֵי מִילָא — נֵימָא מִיל וּמֶחֱצָה. אֶלָּא תְּלָתָא תִּילְתֵי מִילָא — נֵימָא מִיל. אֶלָּא: תְּלָתָא רִיבְעֵי מִילָא. וְרַב יוֹסֵף אָמַר רַב יְהוּדָה אָמַר שְׁמוּאֵל: שְׁנֵי חֶלְקֵי מִיל. מַאי שְׁנֵי חֶלְקֵי מִיל? אִילֵימָא תְּרֵי פַּלְגֵי מִילָא — לֵימָא מִיל. וְאֶלָּא תְּרֵי רִבְעֵי מִילָא — לֵימָא חֲצִי מִיל. אֶלָּא

Nevertheless, the definition of twilight is uncertain. And what is twilight? From when the sun sets, as long as the eastern face of the sky is reddened by the light of the sun. If the lower segment of the sky has lost its color, and the upper segment has not yet lost its color, that is the twilight period. If the upper segment has lost its color, and its color equals that of the lower one, it is night; this is the statement of Rabbi Yehuda. Rabbi Neḥemya says: The duration of the twilight period is the time it takes for a person to walk half a mil after the sun sets. Rabbi Yosei says: Twilight does not last for a quantifiable period of time; rather, it is like the blink of an eye: This, night, enters and that, day, leaves, and it is impossible to calculate it due to its brevity. And the Gemara remarks: In this dispute over the precise definition of twilight both Rabba and Rav Yosef follow their line of reasoning stated elsewhere. As it was stated: What is the measure of the duration of twilight? Rabba said that Rav Yehuda said that Shmuel said: The time it takes to walk three parts of a mil. The Gemara asks: What is the meaning of three parts of a mil? If you say that it refers to three halves of a mil, let him say a mil and a half. Rather, if you say that it means three-thirds of a mil, let him simply say one mil. Rather, it means three-quarters of a mil. And Rav Yosef said that Rav Yehuda said that Shmuel said: The duration of twilight is two parts of a mil. Again the Gemara asks: What is the meaning of two parts of a mil? If you say that it means two halves of a mil, let him simply say one mil. Rather, if you say that it means two-quarters of a mil, let him say instead: Half of a mil. Rather,

מֵאֵימָתַי קוֹרִין אֶת שְׁמַע בְּעַרְבִית. מִשָּׁעָה שֶׁהַכֹּהֲנִים נִכְנָסִים לֶאֱכֹל בִּתְרוּמָתָן, עַד סוֹף הָאַשְׁמוּרָה הָרִאשׁוֹנָה, דִּבְרֵי רַבִּי אֱלִיעֶזֶר. וַחֲכָמִים אוֹמְרִים, עַד חֲצוֹת. רַבָּן גַּמְלִיאֵל אוֹמֵר, עַד שֶׁיַּעֲלֶה עַמּוּד הַשָּׁחַר. מַעֲשֶׂה שֶׁבָּאוּ בָנָיו מִבֵּית הַמִּשְׁתֶּה, אָמְרוּ לוֹ, לֹא קָרִינוּ אֶת שְׁמַע. אָמַר לָהֶם, אִם לֹא עָלָה עַמּוּד הַשַּׁחַר, חַיָּבִין אַתֶּם לִקְרוֹת. וְלֹא זוֹ בִּלְבַד, אֶלָּא כָּל מַה שֶּׁאָמְרוּ חֲכָמִים עַד חֲצוֹת, מִצְוָתָן עַד שֶׁיַּעֲלֶה עַמּוּד הַשָּׁחַר. הֶקְטֵר חֲלָבִים וְאֵבָרִים, מִצְוָתָן עַד שֶׁיַּעֲלֶה עַמּוּד הַשָּׁחַר. וְכָל הַנֶּאֱכָלִים לְיוֹם אֶחָד, מִצְוָתָן עַד שֶׁיַּעֲלֶה עַמּוּד הַשָּׁחַר. אִם כֵּן, לָמָּה אָמְרוּ חֲכָמִים עַד חֲצוֹת, כְּדֵי לְהַרְחִיק אֶת הָאָדָם מִן הָעֲבֵרָה: מֵאֵימָתַי קוֹרִין אֶת שְׁמַע בְּשַׁחֲרִית. מִשֶּׁיַּכִּיר בֵּין תְּכֵלֶת לְלָבָן. רַבִּי אֱלִיעֶזֶר אוֹמֵר, בֵּין תְּכֵלֶת לְכַרְתִּי. וְגוֹמְרָהּ עַד הָנֵץ הַחַמָּה. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, עַד שָׁלֹשׁ שָׁעוֹת, שֶׁכֵּן דֶּרֶךְ בְּנֵי מְלָכִים לַעֲמֹד בְּשָׁלֹשׁ שָׁעוֹת. הַקּוֹרֵא מִכָּאן וְאֵילָךְ לֹא הִפְסִיד, כְּאָדָם הַקּוֹרֵא בַתּוֹרָה:

The beginning of tractate Berakhot, the first tractate in the first of the six orders of Mishna, opens with a discussion of the recitation of Shema, as the recitation of Shema encompasses an acceptance of the yoke of Heaven and of the mitzvot, and as such, forms the basis for all subsequent teachings. The Mishna opens with the laws regarding the appropriate time to recite Shema: From when, that is, from what time, does one recite Shema in the evening? From the time when the priests enter to partake of their teruma. Until when does the time for the recitation of the evening Shema extend? Until the end of the first watch. The term used in the Torah (Deuteronomy 6:7) to indicate the time for the recitation of the evening Shema is beshokhbekha, when you lie down, which refers to the time in which individuals go to sleep. Therefore, the time for the recitation of Shema is the first portion of the night, when individuals typically prepare for sleep. That is the statement of Rabbi Eliezer. The Rabbis say: The time for the recitation of the evening Shema is until midnight. Rabban Gamliel says: One may recite Shema until dawn, indicating that beshokhbekha is to be understood as a reference to the entire time people sleep in their beds, the whole night. The mishna relates that Rabban Gamliel practiced in accordance with his ruling. There was an incident where Rabban Gamliel’s sons returned very late from a wedding hall. They said to him, as they had been preoccupied with celebrating with the groom and bride: We did not recite Shema. He said to them: If the dawn has not yet arrived, you are obligated to recite Shema. Since Rabban Gamliel’s opinion disagreed with that of the Rabbis, he explained to his sons that the Rabbis actually agree with him, and that it is not only with regard to the halakha of the recitation of Shema, but rather, wherever the Sages say until midnight, the mitzva may be performed until dawn. Rabban Gamliel cites several cases in support of his claim, such as the burning of fats and limbs on the altar. Due to the quantity of offerings each day, the priests were often unable to complete the burning of all of the fats and limbs, so they continued to be burned into the night, as it is written: “This is the law of the burnt offering: The burnt offering shall remain upon the pyre on the altar all night until morning, while the fire on the altar burns it” (Leviticus 6:2). And, with regard to all sacrifices, such as the sin-offerings and the guilt-offerings that are eaten for one day and night; although the Sages state that they may be eaten only until midnight, by Torah law they may be eaten until dawn. This is in accordance with the verse: “On the day on which it is offered must you eat. Do not leave it until the morning” (Leviticus 7:15). If so, why did the Sages say that they may be eaten only until midnight? This is in order to distance a person from transgression, as if one believes that he has until dawn to perform the mitzva, he might be negligent and postpone it until the opportunity to perform the mitzva has passed. From when does one recite Shema in the morning? From when a person can distinguish between sky-blue [tekhelet] and white. Rabbi Eliezer says: From when one can distinguish between sky-blue and leek-green. And one must finish reciting Shema until the end of the period when you rise, i.e., sunrise, when the sun begins to shine. Rabbi Yehoshua says: One may recite the morning Shema until three hours of the day, which this is still considered when you rise, as that is the habit of kings to rise from their sleep at three hours of the day. While there is a set time frame for the recitation of Shema, one who recites Shema from that time onward loses nothing. Although he does not fulfill the mitzva of reciting of Shema at its appointed time, he is nevertheless considered like one who reads the Torah, and is rewarded accordingly.

אָמַר רָבָא: שִׁיתָּא אַלְפֵי פַּרְסֵי הָוֵי עָלְמָא, וְסוּמְכָא דִרְקִיעָא אַלְפָּא פַּרְסֵי. חֲדָא גְּמָרָא, וַחֲדָא סְבָרָא. סָבַר לַהּ כִּי הָא דְּאָמַר רַבָּה בַּר בַּר חָנָה אָמַר רַבִּי יוֹחָנָן: כַּמָּה מַהֲלַךְ אָדָם בֵּינוֹנִי בַּיּוֹם — עֶשֶׂר פַּרְסָאוֹת: מֵעֲלוֹת הַשַּׁחַר וְעַד הָנֵץ הַחַמָּה חֲמִשָּׁה מִילִין, מִשְּׁקִיעַת הַחַמָּה עַד צֵאת הַכּוֹכָבִים חֲמִשָּׁה מִילִין, נִמְצָא עוֹבְיוֹ שֶׁל רָקִיעַ אֶחָד מִשִּׁשָּׁה בַּיּוֹם. מֵיתִיבִי, רַבִּי יְהוּדָה אוֹמֵר: עוֹבְיוֹ שֶׁל רָקִיעַ אֶחָד מֵעֲשָׂרָה בַּיּוֹם. תֵּדַע, כַּמָּה מַהֲלַךְ אָדָם בֵּינוֹנִי בַּיּוֹם — עֶשֶׂר פַּרְסָאוֹת, וּמֵעֲלוֹת הַשַּׁחַר עַד הָנֵץ הַחַמָּה אַרְבַּעַת מִילִין, מִשְּׁקִיעַת הַחַמָּה וְעַד צֵאת הַכּוֹכָבִים אַרְבַּעַת מִילִין, נִמְצֵאת עוֹבְיוֹ שֶׁל רָקִיעַ אֶחָד מֵעֲשָׂרָה בַּיּוֹם. תְּיוּבְתָּא דְרָבָא, תְּיוּבְתָּא דְעוּלָּא. תְּיוּבְתָּא.

The discussion above pertaining to the distance that an average person can walk in a day is based on the assumption that he walks five mil between dawn and sunrise. The Gemara brings support for this assumption. Rava said: The size of the world is six thousand parasangs, and the thickness of the firmament is one thousand parasangs. One of these measurements with regard to the size of the world is a tradition, and one of the measurements is based upon Rava’s own reasoning. The Gemara explains: Rava holds like that statement which Rabba bar bar Ḥana said that Rabbi Yoḥanan said: How far can an average person walk in a day? One can walk ten parasangs, which are forty mil. This is explained: From dawn until sunrise one can walk a distance of five mil; from sunset until the emergence of the stars one can walk another five mil. Therefore, it is found that the thickness of the firmament is one-sixth of the distance that the sun travels during the day. Between sunrise and sunset, the sun travels a distance of six thousand parasangs during the amount of time an average person can walk thirty mil. During the dawn and twilight periods in the morning and evening, when the sun passes through the thickness of the firmament, an average person can walk five mil, which is one-sixth of the distance he can walk between sunrise and sunset. Consequently, during dawn and twilight the sun must also travel one-sixth of the distance it travels between sunrise and sunset, i.e., one thousand parasangs, which is the thickness of the firmament. The Gemara raises an objection from the following baraita: Rabbi Yehuda says: The thickness of the firmament is only one-tenth of the distance that the sun travels during the day. Know that this is true because how far can an average person walk in a day between dawn and the emergence of the stars? One can walk ten parasangs, which are forty mil, and from dawn until sunrise one can walk only four mil, which are one parasang. Therefore, it is found that the thickness of the firmament is only one-tenth of the distance that the sun travels during the day. This is a refutation of the opinion of Rava. Similarly, it is a refutation of the opinion of Ulla, who holds that an average person can walk fifteen mil in half a day, whereas Rabbi Yehuda holds that the average person can walk sixteen mil in half a day. The Gemara concludes: It is indeed a conclusive refutation.

אָמַר אַבָּיֵי: כְּשֶׁתִּמְצָא לוֹמַר, לְדִבְרֵי רַבִּי מֵאִיר — אֵין אָדָם טוֹעֶה וְלֹא כְּלוּם; לְדִבְרֵי רַבִּי יְהוּדָה — אָדָם טוֹעֶה חֲצִי שָׁעָה. לְדִבְרֵי רַבִּי מֵאִיר — אֵין אָדָם טוֹעֶה וְלֹא כְּלוּם: מַעֲשֶׂה כִּי הֲוָה, בְּמִיפַּק תַּרְתֵּי וּמְעַיֵּיל תְּלָת. וְהָא דְּקָאָמַר שְׁתַּיִם — בְּסוֹף שְׁתַּיִם, וְהָא דְּקָאָמַר שָׁלֹשׁ — בִּתְחִלַּת שָׁלֹשׁ. לְדִבְרֵי רַבִּי יְהוּדָה — אָדָם טוֹעֶה חֲצִי שָׁעָה: מַעֲשֶׂה כִּי הֲוָה, בְּפַלְגָא דְאַרְבַּע הֲוָה, וְהַאי דְּקָאָמַר שָׁלֹשׁ — בְּסוֹף שָׁלֹשׁ, וְקָטָעֵי פַּלְגָא דְשַׁעְתָּא לְקַמֵּיהּ. וְהַאי דְּקָאָמַר חָמֵשׁ — בִּתְחִלַּת חָמֵשׁ, וְקָטָעֵי פַּלְגָא דְשַׁעְתָּא לַאֲחוֹרֵיהּ.

Abaye said: When analyzing the matter, you will find that you can say that according to the statement of Rabbi Meir a person does not err at all, as Rabbi Meir assumes that people know the exact time of day. According to the statement of Rabbi Yehuda a person errs up to half an hour. Abaye elaborates: According to the statement of Rabbi Meir, a person does not err at all, and the reason that in the case where one says two hours and one says three the testimony is valid is that the incident actually occurred as the second hour ended and the third hour began. And when this witness said it happened in the second hour he was referring to the end of the second hour. When that witness said the third hour he was referring to the beginning of the third hour. It is possible that both witnesses spoke the truth. Abaye continues his explanation: According to the statement of Rabbi Yehuda, a person errs by half an hour, as when the incident occurred, it occurred at the midpoint of the fourth hour, at three and a half hours of the day. And this witness, who says three hours, means the end of the third hour, and he errs by saying that it occurred half an hour before the incident actually occurred. And that witness, who says five hours, means the beginning of the fifth hour, i.e., the end of the fourth hour, and he errs by saying that it occurred half an hour after the incident actually occurred. Since it is possible that their testimonies do not conflict, their testimony is valid.

אֶלָּא מַאי, ״עַד וְעַד בַּכְּלָל״? קַשְׁיָא רֵישָׁא, מַאי אִיכָּא בֵּין רַבִּי יְהוּדָה לְרַבָּנַן?! — מִי סָבְרַתְּ דְּהַאי ״פְּלַג מִנְחָה״ פְּלַג אַחֲרוֹנָה קָאָמַר? פְּלַג רִאשׁוֹנָה קָאָמַר, וְהָכִי קָאָמַר: אֵימַת נָפֵיק פְּלַג רִאשׁוֹנָה וְעָיֵיל פְּלַג אַחֲרוֹנָה — מִכִּי נָפְקִי אַחַת עֶשְׂרֵה שָׁעוֹת חָסֵר רְבִיעַ. וְעַל תָּמִיד שֶׁל שַׁחַר שֶׁקָּרֵב בְּאַרְבַּע שָׁעוֹת, מַאן תְּנָא לְהָא דִּתְנַן: ״וְחַם הַשֶּׁמֶשׁ וְנָמָס״, בְּאַרְבַּע שָׁעוֹת.

Rather, what is the alternative? That until means until and including? Then the first clause of the mishna is difficult, as explained above with regard to the midpoint of the afternoon: What is the halakhic difference between the opinion of Rabbi Yehuda and the opinion of the Rabbis? The Gemara answers: Do you think that when this midpoint of the afternoon was mentioned it was speaking of the period following the midpoint, the last part of the afternoon, from an hour-and-a-quarter before sunset until sunset? This was not the intention. Rather, it was speaking of the period prior to the midpoint, the first part of the afternoon, which, as explained above, is from nine-and-a-half hours after sunrise until an hour-and-a-quarter before sunset. Consequently, until the midpoint of the afternoon means until the end of the first half of that afternoon period. And this is what he is saying: When does the first half leave and the second half enter? From when eleven hours minus a quarter have passed since sunrise. Rabbi Yehuda’s use of the term until always means until and including. And about the daily morning offering that was sacrificed at four hours. Based on this, the Gemara attempts to identify the tanna who taught that which we learned in the mishna about the manna that fell for the children of Israel in the desert: “And they gathered it morning by morning, each according to what he eats, and when the sun grew hot it melted” (Exodus 16:21); that took place four hours into the day.

הָתָם לָא שְׁכִיחָא שִׁכְרוּת, הָכָא שְׁכִיחָא שִׁכְרוּת. אִי נָמֵי, בְּמִנְחָה — כֵּיוָן דִּקְבִיעָא לַהּ זִימְנָא מִירְתַת וְלָא אָתֵי לְמִפְשַׁע. עַרְבִית — כֵּיוָן דְּכוּלֵּהּ לֵילְיָא זְמַן עַרְבִית, לָא מִירְתַת וְאָתֵי לְמִפְשַׁע. מַתְקִיף לַהּ רַב שֵׁשֶׁת: טְרִיחוּתָא לְמֵיסַר הֶמְיָינֵיהּ?! וְעוֹד, לֵיקוּ הָכִי וְלִיצַלֵּי! — מִשּׁוּם שֶׁנֶּאֱמַר: ״הִכּוֹן לִקְרַאת אֱלֹהֶיךָ יִשְׂרָאֵל״.

The Gemara responds that there is a difference between the cases. There, at the time of the afternoon prayer, drunkenness is uncommon, as it is unusual to drink excessively during the day. However, here, in the case of the evening prayer, drunkenness is common, and therefore there was room to issue a decree requiring one to interrupt his meal to recite the evening prayer. Alternatively, it is possible to explain that with regard to the afternoon prayer, since its time is fixed, he is anxious, and he won’t come to be negligent and forget to pray. However, with regard to the evening prayer, since all night is the time for the evening prayer, he is not anxious, and he will come to be negligent. Rav Sheshet strongly objects to this: Is it a burden to tie his belt? In addition, if it is a burden, let him stand that way, without a belt, and pray. The Gemara answers: It is necessary to wear a belt while praying, since it is stated: “Prepare to greet your God, Israel” (Amos 4:12). One must prepare and adorn himself when standing before God.

ספק חשכה ספק אינה חשכה אין מעשרין את הודאי ואין מטבילין את הכלים ואין מדליקין את הנרות והוא בין השמשות שהוא ספק יום ספק לילה וזמנו משתשקע החמה ואילך (עי' סי' רצ"ג ותר"ח) ומי שאינו בקי בשיעור בין השמשות ימהר להדליק כדאמר ליה רבה לאריסיה אתון דלא קים לכו בשיעורא דרבנן אדאיכא שימשא בריש דיקלא אדליקו שרגא פי' בעוד השמש בראש האילנות וביום המעונן במתא חזו תרנגולין שיושבין על הקורה מבע"י בדברא חזו עורבי שגם הם יושבין מבע"י א"נ אירנא פירוש עשב שעליו נוטין לרוח השמש שחרית נוטין למזרח בחצי היום זקופין ערבית נוטין למערב: אבל מעשרין את הדמאי ומערבין עירובי חצירות אבל לא עירובי תחומין:

וְאֵי זֶה הוּא זְמַנָּה בַּיּוֹם. מִצְוָתָהּ שֶׁיַּתְחִיל לִקְרוֹת קֹדֶם הָנֵץ הַחַמָּה כְּדֵי שֶׁיִּגְמֹר לִקְרוֹת וּלְבָרֵךְ בְּרָכָה אַחֲרוֹנָה עִם הָנֵץ הַחַמָּה. וְשִׁעוּר זֶה כְּמוֹ [עִשּׂוּר] שָׁעָה קֹדֶם שֶׁתַּעֲלֶה הַשֶּׁמֶשׁ. וְאִם אִחֵר וְקָרָא קְרִיאַת שְׁמַע אַחַר שֶׁתַּעֲלֶה הַשֶּׁמֶשׁ יָצָא יְדֵי חוֹבָתוֹ שֶׁעוֹנָתָהּ עַד סוֹף שָׁלֹשׁ שָׁעוֹת בַּיּוֹם לְמִי שֶׁעָבַר וְאִחֵר:

When is the proper time [for the recitation of the Shema] during the day? The commandment is that one should start to read before sunrise in order to conclude and recite the last blessing with the sunrise. This measure [of time] is one-tenth of an hour before the sun rises. A person who delays and reads the Shema after the sun rises fulfills his obligation, for the proper time is until the end of the third hour of the day for one who transgresses and delays.

ואע"ג דאיפליגו אמוראי בפירוש דברי רבי יהודה כבר פסקו הרי"ף והרא"ש והרמב"ם בפ"ה דהלכה כרבה דאמר דה"ק איזהו בין השמשות משתשקע החמה וכל זמן שפני מזרח מאדימין והכסיף התחתון ולא הכסיף העליון נמי בין השמשות ומפרש בגמרא דלדידיה הוי שיעור בין השמשות תלתא רבעי מיל וזהו שכתב רבינו בסימן תר"ח דזמן בין השמשות הוא אלף ות"ק אמות קודם הלילה.

(א) בין השמשות - ואם נסתפק אם הגיע הזמן לבה"ש ג"כ אסור:

ספק חשיכה והיא בין השמשות (היינו כדי שיעור הלוך ג' רבעי מיל אחר שקיעת החמה (טור בסי' רצ"ג וכדלקמן ס"ס ב') [ושיעור מיל הוא שליש שעה פחות חלק ל'] אין מעשרים את הודאי ואין מטבילין את הכלים ואין מדליקין את הנרות ואין מערבין עירובין תחומין (וע"ל סי' תט"ו ס"ב) אבל מעשרין את הדמאי וטומנין את החמין ומערבין עירובי חצרות (וע"ל סי' שצ"ג) ומות' לומר לעכו"ם בין השמשות להדליק נר לצורך שבת וכן לומר לו לעשות כל מלאכה שהיא לצורך מצוה או שהוא טרוד ונחפז עליה:

הגה ומשערינן שעות אלו לפי ענין היום ואף אם היום ארוך משערינן לי"ב שעות והם נקראים שעות זמניות וכן כל מקום ששערו חכמים בשעות משערינן בשעות אלו (רמב"ם בפי' המשנה בפ"ק דברכות) ואסיקנא דעבד כמר עבד ודעבד כמר עבד והוא שיעשה לעולם כחד מינייהו שאם עושה כרבנן ומתפלל מנחה עד הלילה שוב אינו יכול להתפלל ערבית מפלג המנחה ולמעלה ואם עושה כר' יהודה ומתפלל ערבית מפלג המנחה ולמעלה צריך ליזהר שלא יתפלל מנחה באותה שעה ועכשיו שנהגו להתפלל תפלת המנחה עד הלילה אין להתפלל תפלת ערבית קודם שקיעת החמה ואם בדיעבד התפלל תפלת ערבית מפלג המנחה ולמעלה יצא ובשעת הדחק יכול להתפלל תפלת ערבית מפלג המנחה ולמעלה:

אמנם בעצם זמן בין השמשות יש מחלוקת בין הפוסקים, דכפי המבואר מהגמרא (שם ל"ד:) הוי זמן בין השמשות משך הילוך ג' רבעי מיל אחר השקיעה, ואחר כך הוי לילה. וכפי שחושבין הילוך מיל לי"ח חלקים מששים בשעה, הוויין ג' חלקים - י"ג חלקים וחצי.