The Halacha below was generated by AI based on multiple classes given by Rabbi Eli Mansour in the Bekiim B'Halacha series. Click on any of the dates below to hear the original audio file. This write-up has been reviewed, but if any errors remain , we welcome corrections. 06-09-25 ; 06-10-25 ; 06-11-25 ; 06-12-25 The Question What happens to the obligation of Tefillin if a person crosses the International Dateline? Should he wear Tefillin twice if he repeats a day? Should he skip Tefillin if he loses a day? This question affects travelers going to or from places like Japan, Australia, Hawaii, or America. Understanding the Issue When one crosses the dateline, he might experience the same calendar day twice or skip a day altogether. For example: • Flying from America to Australia on a Thursday evening can result in arriving on Saturday morning , skipping Friday entirely. • Flying from Australia to America can cause one to repeat Friday twice. This brings up a Halachic dilemma: Do I wear Tefillin both times I experience Friday? Or do I wear Tefillin on a day I missed ? Obligation Based on Personal Count According to many Poskim , Tefillin should be worn based on your personal count of days —not the calendar date printed in the location. If you have experienced six consecutive days with Tefillin, and the next is your seventh, you do not wear Tefillin, as it is your Shabbat . If you have not yet reached your Shabbat (because you skipped a day due to travel), you do wear Tefillin on the local Shabbat, as it is your sixth day . This concept is based on the Gemara's case of a person lost in the desert , who forgets what day it is. He wears Tefillin for six days and rests on the seventh. The Misva follows his personal sequence. Local Calendar vs. Personal Reality While some argue to follow the local calendar—since the place is observing Shabbat or Yom Tob—many authorities rule that your obligation to wear Tefillin follows your own timeline . This means: • If you fly and miss Friday: On the local Shabbat, you wear Tefillin. • If you fly and repeat Friday: You wear Tefillin both days, since for you they are two different days. Beracha or Not ? Some suggest wearing Tefillin without a Beracha in cases of uncertainty—such as when repeating a day or wearing Tefillin on the local Shabbat. • If you're unsure, don Tefillin without saying the Beracha. • If possible, listen to someone else's Beracha and respond Amen. Tefillin vs. Tefila This discussion is about Tefillin , not Tefila . The prayers of the day must follow the local calendar . If the community is praying Shabbat prayers, you follow them. But for Tefillin, the obligation follows your own count of six days of labor. Summary • The obligation to wear Tefillin follows your personal six-day cycle , not the local calendar. • If you skipped a day via travel, wear Tefillin on the local Shabbat. • If you repeat a day, wear Tefillin both times. • When in doubt, wear Tefillin without a Beracha . • Tefila (prayer) follows the local calendar, while Tefillin follows your own timeline.