Rules for Overnight Shift Work Hour Calculation

An overnight shift that crosses midnight is one continuous work period, not two separate workdays. Federal FLSA overtime is calculated by the workweek, so the hours count toward the weekly 40-hour threshold regardless of which calendar day the shift ends on. The key is correct clock-time math and a fixed workweek definition.

The Cross-Midnight Math

Calculating hours for an overnight shift is straightforward once you handle the date change. If the start time is later in the day than the end time, add 24 to the end time before subtracting.

Worked Example

A worker clocks in at 10:00 PM Monday and clocks out at 6:00 AM Tuesday.

The shift is 8 hours of paid work, all in a single continuous period.

For shifts under 24 hours, this method always works. For shifts over 24 hours — rare but possible in some on-call roles — track total elapsed time directly.

Splitting Paid and Unpaid Breaks

An overnight meal break is handled the same way as a daytime one. A bona fide 30-minute meal where the worker is fully relieved of duty can be unpaid.

Example: A worker clocks in at 10:00 PM, takes an unpaid 30-minute meal from 2:00 AM to 2:30 AM, and clocks out at 6:30 AM.

• Total elapsed time: 10:00 PM to 6:30 AM = 8.5 hours
• Unpaid meal: 0.5 hours
• Paid hours: 8.0 hours

At $22/hour, that shift equals $176 in gross pay.

The FLSA Workweek Concept

This is the part that causes the most confusion. Under 29 CFR 778.105, an FLSA workweek is a fixed and regularly recurring period of 168 hours — seven consecutive 24-hour days. It does not have to align with a calendar week.

Key rules:

• The workweek can begin on any day and at any hour.
• Once set, the workweek stays fixed. Employers cannot change it from week to week to avoid overtime.
• Each workweek stands alone. Hours cannot be averaged across two workweeks.

Defining the Workweek

A hospital running 24/7 might define its workweek as Sunday 12:00 AM through Saturday 11:59 PM. A manufacturer might use Monday 6:00 AM through the following Monday 5:59 AM to align with its shift schedule.

The start time matters because it determines which hours fall in which workweek. An overnight shift that starts Sunday at 10:00 PM and ends Monday at 6:00 AM falls entirely in the workweek that contains Sunday 10:00 PM — assuming the workweek starts Sunday 12:00 AM.

Overtime Triggers by the Week, Not the Day

Under federal FLSA, overtime is owed only for hours worked over 40 in the workweek. A worker who logs four 10-hour overnight shifts has 40 hours and no overtime. Add a fifth 8-hour shift and the last 8 hours pay at 1.5× the regular rate.

Worked Example

A worker logs the following overnight shifts, all in the same workweek:

The first 40 hours pay at straight time. The remaining 6 hours pay at 1.5× the regular rate.

At $22/hour base:

• Straight time: 40 × $22 = $880
• Overtime: 6 × $33 = $198
• Weekly gross: $1,078

State Rules with Daily Overtime

Federal law is weekly, but a handful of states add daily overtime rules that change the math for overnight workers.

California Labor Code § 510 requires:

• 1.5× for hours over 8 in a day.
• 2.0× for hours over 12 in a day.
• 1.5× for the first 8 hours on the 7th consecutive day in a workweek.
• 2.0× for hours beyond 8 on the 7th consecutive day.

For California overnight workers, an 8-hour shift crossing midnight still counts as one workday for daily overtime purposes — the workday is defined by the employer and must be documented. Hours over 8 in that workday trigger daily overtime, even if total weekly hours are under 40.

Other states with daily overtime provisions include Alaska, Nevada, Oregon (for manufacturing), and Puerto Rico.

Common Errors to Avoid

Three mistakes show up regularly in overnight shift payroll:

1. Splitting a continuous shift across two workweeks. A shift that starts in one workweek and ends in the next is one continuous work period, but the hours are allocated to the workweek in which they were worked.
2. Treating the calendar day as the workday. Unless the employer has defined a non-standard workday, an overnight shift that crosses midnight still belongs to a single workday for daily overtime purposes in states like California.
3. Averaging hours across weeks. Two 30-hour weeks cannot be averaged to 30 per week to avoid overtime in a 50-hour week. Each workweek stands alone.

Tracking Overnight Hours

Keep a daily log with clock-in, clock-out, and meal break times. Note which workweek each shift belongs to based on your employer’s defined workweek start. Run your weekly hours through the Shift Work Calculator to confirm the cross-midnight math, then verify against your pay stub using the Time Card Calculator.