Edit time

I would like to synchronize my audio file with external events, which have been marked by their time of occurence. For instance I started the record precisely at 22:30.
How can I have my displayed signal start at a time different from zero (say, here 22:30) ?
Is there a possibility to edit time labels, or to make a time shift like for recording ?

You could add a point label with the start time … http://manual.audacityteam.org/man/Label_Tracks
NB: the recording can progressively go out of sync with real-time, depending on the performance of your computer.


Well, I already thought of labelling the start time.
But labels are text, not numbers, and I would like to identify all the following events by their exact time of occurence.
Of course I could take the exact occurence time, substract the start time, and search for that difference in Audacity, but it’s not very convenient.