I've got a server which generates some metrics for a period 9AM – 12AM. Items is generated from LLD and lost resources kept for 30 days. Most of items live only for one day, so if trigger does not go off before midnight it stays in 'problem' state until it deleted in 30 days, this kind of triggers is acknowledged manually in the evening.
To prevent zabbix from alerting unacknowledged stuck triggers all night long there is a time period condition in action that sends emails – 1-5,09:00-23:55. If trigger was ack'ed zabbix starts to send emails after 23:55 and never stops until trigger is disabled/deleted.
How to reproduce:
1) Create LLD rule with some items and triggers
2) Create action with time period
3) Wait for LLD and items creation
4) Make trigger go on
5) Force item to become 'Not supported' (Received value [] is not suitable for value type [Numeric (float)])
6) Ack the trigger
7) Wait for action time period to end, zabbix will start to alert.