How to Calculate Overnight Shift Hours

Counting across midnight

Subtracting the In from the Out does not work when the Out is the next morning: 6:30 AM minus 10:00 PM comes out negative. Count the two parts instead. From 10:00 PM to midnight is 2:00; from midnight to 6:30 AM is 6:30; together they make 8:30. Take off an unpaid 30-minute break and the shift is 8:00, or 8.00 decimal hours.

With times written on the 24-hour clock, the trick is to add a whole day to the Out: 06:30 + 24:00 = 30:30, and 30:30 − 22:00 = 8:30. The calculator does this by itself. Whenever an Out is earlier than its In, it reads the Out as the next morning, and the worked arithmetic shows it:

• Mon: 10:00 PM → 6:30 AM (next day) = 8:30, − 30 min break = 8:00 (480 min ÷ 60 = 8.00 h)

Which day the hours go on

A night shift touches two calendar days, but a time card has one row for it. The three payroll offices quoted below put the shift's hours on the day it starts by default:

• For shifts that cross over midnight, the time will be recorded on the day the shift started. (Oregon State University, MyTime timesheet rules)
• time worked and time away from work with pay are reported on the workday that the shift begins in order to avoid having to split the hours across two days (Duke University Finance, GAP 101.51)
• Total hours will populate at the top of the timesheet on the day the shift started. (third-shift time entry guidance published on montgomerycollege.edu)

CardHours does the same: a Friday night shift that ends on Saturday morning counts on Friday.

When the break splits the shift

Some cards record the break as two separate pairs of times. Montgomery College's third-shift guidance shows one: 10:00pm to 2:00am, then 2:30am to 6:30am (third-shift time entry guidance published on montgomerycollege.edu). The second pair starts after the first ends, so it is also on the next morning, and the day is the two pairs added:

• Thu: 10:00 PM → 2:00 AM (next day) = 4:00, + 2:30 AM → 6:30 AM = 4:00, = 8:00 (480 min ÷ 60 = 8.00 h)

In the calculator, tap + Split on the row to get the second In and Out. Typing the gap as a 30-minute break on a single 10:00 PM to 6:30 AM pair gives the same 8:00.

Five nights in a row

Montgomery College's sample third-shift schedule is Sample Schedule: Monday-Friday, 10:00 p.m.-6:30 a.m. (third-shift time entry guidance published on montgomerycollege.edu). With a 30-minute break each night, the five shifts add up as below; Friday's shift ends on Saturday morning and still counts on Friday.

The week comes to 40:00. Montgomery College itself splits only the Friday night, at the end of its work week: The official work week ends on Friday, so the 1st entry should be the start of the shift (In) to 12:00am (third-shift time entry guidance published on montgomerycollege.edu). Some employers split a shift at midnight; to match such a card, enter the two parts on two rows.

Midnight is 12:00 AM

NIST notes that 12 a.m. and 12 p.m. are ambiguous and should not be used. (NIST, Times of Day FAQs). On CardHours, 12:00 AM is midnight at the start of a day and 12:00 PM is noon, and the field shows a small midnight or noon next to them. You can also type 24:00 for the end of a day, or switch the card to the 24-hour clock.

Clock changes are the one case the method cannot see. The calculator takes the difference of the clock times, so on the night daylight saving time starts or ends, the time actually spent is an hour more or less than the card shows; adjust that row by hand. The other limits are listed on How we calculate.