The sub_time(timefield, minutes) function appears in the Use Function dropdown of the CRM expression formula builder and can be used to subtract a specified number of minutes from a time field. However, this function is not documented in the official Dazos Expressions User Guide, and its behavior may be inconsistent or unreliable in some scenarios.

This article explains what the function does, how to locate it, and what alternatives are available if you need stable, predictable results.

You may want to calculate a time value that is a set number of minutes before a recorded time — for example, displaying or storing a time that is 30 minutes before an appointment or intake time field.

The sub_time() function is the available option within CRM expressions for this purpose, but customers should be aware of its limitations before relying on it in production configurations.

⚠️ Important: Because sub_time() is not officially documented, its behavior may be inconsistent or produce unexpected results in certain configurations. It is not a fully confirmed supported feature.

💡 Tip: If you need reliable and stable time subtraction results, the recommended alternative is to calculate the adjusted time value outside of CRM expressions — for example, via an API workflow or in the source system that sends the value — and then save the pre-calculated result to the field.

✅ Best Practice: Test sub_time() thoroughly in a non-production or test record before using it in live workflows or reports to confirm it behaves as expected in your specific use case.

If consistent and predictable time arithmetic is critical, handle the calculation externally before the value reaches Dazos CRM:

This approach avoids any uncertainty related to expression engine behavior with time values.