<mention to the bot> <time like 5m1s> <message>
<mention to the bot> <date and/or time> <message>
@RemindBot 10d message
- sendmessage
after 10 days@RemindBot 1h1m1s message
- sendmessage
after 1 hour 1 minute 1 second@RemindBot 22:33:44 message
- sendmessage
at today at 22:33:44@RemindBot 2021/12/31 message
- sendmessage
at 2021/12/31 (and same time)