Adding minutes to a Timestamp

Maybe this is common knowledge, but I just figured it out.

The TIME_ADD function is usually used to add hours to a Timestamp.

But it can also be used to add minutes. Just use a fraction for the second parameter.

For example, to add 1 minute to a Timestamp do the following:
TIME_ADD(theTimeStamp,0.166667)

I am not sure what precision is necessary or best.

oops, I misplaced the decimal point. The above will add 10 minutes.
To add just 1 minute it should be:

TIME_ADD(theTimeStamp,0.016667)

Subtracting doesn't work for me, any suggestions?

eg.
TIME_ADD(theTimeStamp,-0.166667)