A time stamp apparatus that carries out e-signature including local time based on the local time output from an internal clock, includes a radio wave time acquiring unit that receives a radio wave including standard time so as to acquire the standard time as radio wave time, an authentication time acquiring unit that acquires authentication time from a time publishing apparatus for publishing the authentication time synchronous with the standard time, and a time correcting unit that corrects the local time using the authentication time based on a difference between the radio wave time and the local time.