Someone asked me about what to do regarding Tefilin. They leave for work just after Alos Hashachar and the nature of their work does not allow them to put on Tefilin during the day. Can they put on Tefilin at night?
Rav Moshe Feinstein (Iggros Moshe, Orach Chaim I, no. 10) discusses this question, and rules that it is permitted for a person going to work early to put on tefillin before he leaves (after he wakes up), even with a berachah.
This is based on the ruling of the Shulchan Aruch (30:3), according to which a person getting up early can put on tefillin before daybreak. Although the Shulchan Aruch rules that the berachah is only recited later, Rav Moshe relies on those opinions that there is no prohibition (even rabbinic) against putting on tefillin at night, and permits even making a berachah.
However, this applies specifically to somebody who has no option but to put on tefillin early, and to take them off before the right time. It is certainly preferable to keep them on until the time has arrived, and then to make the berachah, if this is possible.
In addition, Rav Moshe writes that his p’sak for making a berachah is for somebody who is not a talmid chacham, who is liable to show disregard for a mitzvah where a berachah is not made. For a talmid chacham, he writes that tefillin should be worn early without making a berachah.