The "amend" command:

Usage: fossil amend HASH OPTION ?OPTION ...?

Amend the tags on check-in HASH to change how it displays in the timeline.

Options:

--author USER

Make USER the author for check-in

-m|--comment COMMENT

Make COMMENT the check-in comment

-M|--message-file FILE

Read the amended comment from FILE

-e|--edit-comment

Launch editor to revise comment

--date DATETIME

Make DATETIME the check-in time

--bgcolor COLOR

Apply COLOR to this check-in

--branchcolor COLOR

Apply and propagate COLOR to the branch

--tag TAG

Add new TAG to this check-in

--cancel TAG

Cancel TAG from this check-in

--branch NAME

Make this check-in the start of branch NAME

--hide

Hide branch starting from this check-in

--close

Mark this "leaf" as closed

-n|--dry-run

Print control artifact, but make no changes

--date-override DATETIME

Set the change time on the control artifact

--user-override USER

Set the user name on the control artifact

DATETIME may be "now" or "YYYY-MM-DDTHH:MM:SS.SSS". If in year-month-day form, it may be truncated, the "T" may be replaced by a space, and it may also name a timezone offset from UTC as "-HH:MM" (westward) or "+HH:MM" (eastward). Either no timezone suffix or "Z" means UTC.