Yes. Daytime only AMs may operate their FM translator 24/7.
From FCC regulations 74.1231:
> (a) FM translators provide a means whereby the signals of AM or FM broadcast
> stations may be retransmitted to areas in which direct reception of such AM or FM
> broadcast stations is unsatisfactory due to distance or intervening terrain barriers,
> and a means for AM Class D stations to continue operating at night.