Timezone change confuses Jenkins

Today we encountered a mess on Jenkins.

The significant issues were:

• Jenkins scheduled multiple builds of the same job in parallel which affected each other and failed quickly
• Newly scheduled builds didn't appear in Build History, as well as the Build Monitor screen on our wall projection

It's actually weird that although Build History doesn't update, when you go to Build Trend you can find them, which implies some underlying inconsistency in Jenkins' implementation.

Finally it's proven that it's caused by timezone change: from Australia/Melbourne to UTC, which confused Jenkins because last build happened in the future!

This apparently also affected Jenkins' change polling mechanism, which made it detected new changes everytime.