all hours

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.
See also: all, and, hour
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

*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.
See also: all, hour
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

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]
See also: all, hour
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
See also:
References in classic literature ?
One sees so many students abroad at all hours, that he presently begins to wonder if they ever have any working-hours.
For employees earning only one rate of pay per hour, you don't need to do any calculation to find the regular rate: That hourly wage is the regular rate, and you pay 1.5 times that amount for all hours over 40 in a workweek.
For most employers, a covered employee must be paid overtime for all hours over 40 worked in a given week.
Under this method, the employee must be paid a salary designed to compensate the employee for all hours worked, and the employee must work a fluctuating number of hours of overtime every week.
Be sure employees are being paid for all hours worked, even before and after scheduled shifts, during scheduled breaks or meal periods, and while attending staff meetings or mandatory training sessions.
The term resident, after all, dates back to the days when young doctors literally lived in the hospital for a few years after they finished medical school, so that they could observe the course of disease at all hours of the day and night.
One is the increase in overall employment (from 68.9 million in 1982 to 69.4 million in 1983) which generally means a larger proportion of junior employees who do not receive as much paid leave time.3 Consequently, the average hours at work as a percent of all hours paid per employee rose.
(Of course, most long-term care facilities can take advantage of Section 7(j) of the FLSA, which allows them to base overtime compensation on work in excess of eighty hours in a fourteen day period, provided they also pay overtime for all hours worked in excess of eight in any given day.) Owners and executives also should be concerned about plans and schemes that provide for compensatory time or "banking" of time for use as time off in a later pay period.