How to Change the Date on an Omega Seamaster
An Omega Seamaster watch displays analogue time and the date, and is powered by normal movement with its self-winding mechanism, or by manual winding if the watch has not been worn for more than two days. You can easily change the date on your Seamaster.
Pull out the crown, the small knob on the right side of the watch, to the second position (first position is flush with the watch; third position is all the way out).
Turn the crown backward until you reach the correct date.
Push the crown back down.