First thing here is that you won't be able to segment customers using campaigns. Segmentation is determined through smart lists built in the segmentation itself.
Regarding your need of querying date values, you can to try to do this in the flow as a choice and use the system token for today's date.
Smart List = Data Value is not empty
Flow Action = Change Data Value
Choice 1 = If Data Value is on or after {{system.dateTime}}
Seems like you could create the following campaign:
Smart List
Cancellation Date is in future after 0 days
Hi,
In case you can't get it to work. I have a tool you could test for field formulas.
Best,
Diederik