One approach is to use at least two fields:
- Define a date field that auto-enters the modification date. Any time you edit that record this field will update to store the current date.
- Define a summary field to return the Maximum of this date field.
If all your records are in the found set (Show All Records) this summary field will return the most recent date any record in the table was edited.
"I would like to track the most recent date that I updated any of them"
Create another occurrence of your table - call it self join. Join this 'copy' to your regular table but use any field on each side (except for containers or summary fields). The fields do NOT have to match because you will be joining them by Cartesian Product. That would be the last join option in the relationship dialog, signified by the X.
This joins all records to itself so you can see across all records. Again from this relationship dialog, check 'sort' on the self join side and specify your Modification Date or Modification Timestamp in descending order.
Now on your reports, place the SelfJoin::Modifcation field in the header (or place it using merge field). It will always display the last time you modified ANY record in your table.