A digital time clock that may be used in conjunction with a mechanical time clock. The digital time clock is placed on or adjacent to an existing mechanical time clock. A radio frequency identification (RFID) tag is associated with each time card that is distributed to employees. As an employee inserts a time card into the mechanical time clock, the digital time clock detects the proximity of the time card and reads the RFID tag. An RFID identifier is stored along with an indication of the time that the identifier was read. The digital time clock may be kept in a low-power standby state until the time card is detected, at which time the digital time clock enters an operational state. The digital time clock may be transported to a location where payroll is to be performed, and data downloaded to a processing device.