When you define or edit the template for the date calculation field, all the records will be updated with the new calculation. This process happens in the background.
After making a change to the template, you should see all the records update with the new calculation. You can try making a temporary change to the calculation template to test this. To get a more detailed view of what is going on, use the plugin debugger to see the result of the calculation on each record.
It’s important to note that if the record doesn’t contain the needed values for the calculation, no change will be made to that record.
It is possible that your server configuration isn’t allowing the background process to work. For example, this can happen with hosting that uses an aggressive cache on the “options” database table.
Thanks for the reply. I resaved the participants and now a change in the template is reflected immediately, but initially the fields returned a 0 or were empty. Anyway it works now.
I noticed some strange behavior with a date calculation like [start_lidmaatschap]+[#25_years]=[?year],
When [start_lidmaatschap] is on first of january it calculates the year minus 1, so 01-jan-2000 will return 2024, while 02-jan-2000 will return 2025. Any idea why that happens?
This can happen when there is a difference in time zone from the WP install and the web server. This article explains how you can deal with that: Date Shifting and Other Timezone-related Issues in Participants Database
