The org-mode default timestamp format does not include timezone information and only hours and minutes of the time are stored.
Because it includes the abbreviate name of the day (%a),
timestamps can’t be compared to each other using string comparison.
They also include spaces which makes it hard to parse the timestamps in the review data table in awk..
To avoid these issues, all timestamps added or used by org-fc are
ISO8601 formatted (e.g. 2020-01-15T11:58:12) using UTC0 as the
timezone.
Use of hydra
To keep this package as small as possible, abo-abo/hydra is used for showing statistics and hotkeys during review.
The main benefit of this is that it saves us from writing a lot of (hard) window / split / buffer management code.
As a consequence, if you want to add your own hotkeys to one of the hydras used by this package, you’ll have to write a new one instead of being able to redefine keys / add keys in an existing one.