Question: When does “day” start, in this regard?
Answer: In this halachic application, day is neither of the two standard daily astronomical occurrences, namely ‘alos hashachar’ (dawn) and ‘haneitz hachama’ (sunrise). Rather, it is somewhere in-between, referred to as ‘misheyakir’ (lit. “from when one can recognize”.) Elsewhere in MBY (89:1 – our first lesson EVER!), we gave the following definition: “Mishyakir - Light enough to see your friend at 4 Amos (cubits) away: Earliest time to make a bracha on talis, tefillin and fulfill Shema.”
Converting that to real minutes, opinions vary. According to the popular website - www.My Zmanim.com - on May 29 in Atlanta, GA, here were the 3 halachic morning times:
‘Alos hashachar’ - 5:16 am
‘Misheyakir’ - 5:37 am
‘Haneitz hachama’ - 6:29 am
Thus we see that, according to a prevalent opinion, ‘misheyakir’ occurs more than 20 minutes after ‘alos hashachar. (Ed: In cases of great urgency, there are earlier interpretations which may be relied upon. Please consult your Rav for a proper halachic ruling.)
Question: Does this mean that a person may not don his talis before ‘misheyakir’?
Answer: No, it doesn’t. He may indeed don it; it’s just that he may not make the bracha until after ‘misheyakir’ and only at an appropriate breaking-point. MBY 54:1-3 Laws pertaining to ‘Yishtabach’ gives the procedure for making the brachos over talis and tefillin in the event that they were donned before ‘misheyakir’. (Ed: Please let me know if you would like me to forward you that lesson.) When the time comes, one should hold his tzitzis, make the bracha and then run his fingers along them. This simulates the proper order of making a bracha and then performing the mitzvah action.