Managing multi-timezone servers

What would be an ideal time and timezone setup for multi-country servers? Especially considering one central IT team managing these servers.

Currently we have each server using a local timezone. e.g. servers in the Chinese datacenter are set with CST. Servers in our German datacenter are set to CEST. Time is set as local time at the datacenter. (note: in total we have servers in 6 countries).
The current setup is useful when it comes to looking at logs locally on the server (knowing exactly when event happened relative to current server local time). However, when looking at events from a central syslog server it becomes a nightmare.

Set everything to UTC. In addition to the examples user48838 mentioned, most things related to aviation are given in Zulu time (same as UTC/GMT). e.g. flight plans are filed with takeoff and landing times in UTC.

GMT (Greenwich Mean Time) is the common time for multiple entities (governments, military organizations, etc.) needing to track time across multiple time zones.