1
general::
Phrase(s): *all hours (of the day and night)
Fig. very late in the night or very early in the morning. (*Typically: until ~; till ~; at ~.) • Why do you always stay out until all hours of the day and night? • I like to stay out till all hours.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Irregular times, as in You can't come home at all hours and expect your supper to be ready. The expression can Also mean "late at night," as in College students like to stay up talking until all hours. It is sometimes amplified into all hours of the day and night. [c. 1930]
American Heritage Idioms