I wanted to (and did) change a number of timestamps by a constant. So I found (and successfully used) org-timestamp-change which starts with (master):
| […] | (defun org-timestamp-change (n &optional what updown suppress-tmp-delay) | "Change the date in the time stamp at point. | The date will be changed by N times WHAT. WHAT can be `day', `month', | `year', `minute', `second'. If WHAT is not given, the cursor position | in the timestamp determines what will be changed. | When SUPPRESS-TMP-DELAY is non-nil, suppress delays like \"--2d\"." | […] Incorrect is the enumeration of valid values for WHAT: 'hour is missing and 'second is probably wrong (?). Incomplete is the documentation for UPDOWN: I had assumed it was the "direction" of change, but that is determined in- stead by the sign of N.
