Many newbie screenwriters use times of day other than DAY or NIGHT in their scene headings.
It looks unprofessional.
DUSK and DAWN are not used in spec scripts by beginning screenwriters unless the kiss by sunset is essential to understanding the story. Filming exteriors with this light is just too expensive because the window of opportunity is so short.
Using the scene heading to help the reader understand when exactly in the day the scene takes place, is really cheating. How do you SEE the difference between MORNING and LATE MORNING on the screen? If the viewers can’t tell, the reader shouldn’t either. If it is essential to the story, present this information visually or in dialogue. The audience won’t see your slug line after all.
If you found this tip useful, check out the Screenplay Checklist, an A-Z of commonly made mistakes by aspiring screenwriters.
Check this 12p. list of errors and annoyances to perfect your spec screenplay.