You can set your digital Timex watch to display military, or 24-hour, time. In other words, 1:00pm would display as 13:00 and 12:30am would display as 00:30. Instructions may vary somewhat between models, with different buttons in different positions, but the general approach is the same.
Press the "MODE" button—usually on the lower left side of the watch, but sometimes on the right center side—to cycle through to the time display.
Press and hold the "SET" button—usually on the right lower side of the watch—until the seconds flash.
Press "MODE" repeatedly to cycle through the displays that flash: from hours to minutes to month to date and day. At the end of the cycle is the hour display option. Make this option flash.
Press the "SPLIT/RESET" button below the face of the watch to change the hour display option to "24-hour display." This is the same as military time. If there is a "NEXT" button on the upper-right side of the watch, use this to advance to the 24-hour option instead of using the "SPLIT/RESET" button. You may need to press a "START/SPLIT" button instead a "SPLIT/RESET" button to cycle between 12- and 24-hour display. The "START/SPLIT" button could be located below the watch face or on the upper-right side of the watch, depending on the model.
Press the "SET" button again. You are now done. All PM hours should be displaying hours between 12 and 23.