rct requests and current system time
In RCT a request with a time t_x that is issued and cannot be answered at t_now is changed to the system time of the first change of the TF tree (t_first_change = t_now).
If the request is answered for the modified, then either:
- you get the wrong transformation
- when requesting the transformation that is one second old at program startup you will probably receive the current one instead of the message that the transform is not available
- you get no transformations at all
- when playing back a tide-file and the transform publisher needs time for the transform calculation, since the current timestamp is probably not included in the tide-file.
Not changing the timestamp will lead to errors for case 1 (what you have to expect nevertheless) and correct results in case 2 (what you have to expect as well).
Disclaimer: Except for if tf itself uses some internal clock, then things might get even weirder.