Managers can reschedule a single meeting occurrence from the actions menu on the My 1:1s page. Only the upcoming (or "current") meeting can be rescheduled.
Once the reschedule option is chosen, a window will appear allowing you to reschedule the single meeting, or change your recurring meeting schedule.
A 1:1 can be rescheduled to a day in the past, as long as it's not before the last completed meeting. It can be rescheduled to any time in the future as long as it is before the date of the next 1:1.
If you have calendar event invitations enabled, when you reschedule the 1:1 meeting the team member will be notified via an updated calendar event.
If calendar event invitations are not enabled, then the meeting change will only appear inside of Uptick and you will need to notify your team member directly.