30:1. The time for (1) laying T'fillin (i.e., placing them upon one's arm and head) in the morning is from the time that one can see a (2) casual acquaintance at a distance of 4 cubits (between 6 and 8 feet) and recognize him.
[This is about an hour before sunrise, but it varies between summer and winter, so one needs a time table.]
30:2. It is prohibited to put on T'fillin (3) at night, because one may forget about them and (4) fall asleep wearing them. If one puts them on (5) before sunset and it becomes dark, even if he remains wearing them (6) the whole night (7) it is permissible, (8) but we do not publicize this. However, If he did not remove his T'fillin after sunset because he had no place to store them safely, (9) and he continues to wear them for the purpose of guarding them, this is permissible and we _do_ publicize this.
30:3. One who wishes (10) to set out on a journey (11) very early in the morning (while it is still dark) (12) lays T'fillin, (13) and when their time arrives (i.e. that of seeing a casual acquaintance at 4 cubits), he should move them on his arm and make the blessing(s), since we are not concerned that one who rose early (14) and set out on a journey will come to sleep in them. MB 10: To set out on a journey - And it is difficult for him to lay them afterwards because of the cold and other such reasons.
30:4. If one was traveling with his tefillin on, (15) and the sun went down, or he was sitting in the house of learning (a Beis Hamidrash) wearing his tefillin (16) and the the sun went down on the eve of Shabbos, he should place his hand over them until he arrives home. If there is a house near a wall that would protect the tefillin, he should remove them and place them there (in the wall).