I am attempting to do a field update every 15 minutes but it seems workflow time triggers start at 1 hour. Is it possible to have workflows execute every 15 minutes?
If not, it is possible to have a countdown timer in an apex class that will execute a piece of code 15 minutes, ultimately acting like a workflow?
Here is an old blog post I saved for this purpose: The 5 minute workflow
It will show you how to set a workflow to fire in intervals of minutes.
BUT: you cannot have it fire say every x minutes. Once a workflow fires it is done unless you reset the field and update the record. If you want something to fire every x minutes, you really should look at implementing a batch process that runs every x minutes and that itself has implications you will need to take into account