General first and last day rule
For qualifying TDY travel, the general rule pays 75% of the applicable M&IE rate for the day of departure from and return to the permanent duty station, regardless of departure or arrival time. The applicable locality can differ between the outbound and return day based on the TDY destination and last TDY location.
Meal rates and orders can change the calculation
Government meal-rate or proportional meal-rate cases do not follow the standard first/last-day calculation in the same way. Furnished meals, authorized exceptions, itinerary changes, and the current Joint Travel Regulations matter. Check orders, DTS, and the servicing office before certifying a voucher.