Sending in item values and their collection times via Zabbix sender is a cool feature. But Unix time stamp format is a bit tricky for human beings and it is easy to get it all wrong.
Currently Zabbix server uses standard atoi() function to convert received time stamp strings to int. This function does not check for any kind of error.
My suggestion is to validate received time stamps stricter. At least we may want to assure that received clock
- is a valid numeric value,
- is not negative,
- does not overflow int type we use in zbx_timestamp_t,
- does not correspond to a time moment from (distant) future.
Maybe we should make validation rules even stricter (let say, server should reject items from distant past) but user should be able to override these extra checks with a special flag to Zabbix sender.