Unfortunately (as you’ve discovered), NOW() doesn’t work the way you want it to work. Even more unfortunately, the basic functionality you wish to build upon doesn’t currently exist in Airtable — namely, field-level timestamps.
To track timestamped values, you have two options: Procedurally require manual setting or update of a date field concurrent with whatever change to base status you wish logged, or re-architect your solution so that each tracked event causes a new record to be generated, as the only autopopulated Airtable field or function with persistence is CREATED_TIME().
(Actually, I guess there is a third option: Use a third-party middleware offering to automate the otherwise manual setting and update of date fields. Typically, these could be handled as two-step functions, which means they can be used even with free Zapier accounts; however, frequency and monthly transaction limits would still apply.)
If I were to try to reengineer your base to allow as nearly automatic timestamping of selfies as possible, I would probably define a [Selfie] table, linked-to from whatever my primary table turned out to be, where every selfie is given its own, freshly generated record. This would allow me to use each record’s CREATED_TIME() as a proxy timestamp for the selfie it contains.
