all hours (of the day and night)
1. A very late hour of the night or very early hour of the morning. You can't call her at all hours of the day and night—that's just rude. Johnny keeps taking the car and staying out till all hours, and I just don't know what to do anymore!
2. All day and night. Is that pharmacy open all hours? I know it's 2 AM, but I just got out of the ER and need to fill a prescription.
*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.
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]