Expensive operation Calendar.getInstance is called on every frame

[Doctoror]

Calendar should be cached as a field instead of method variable, see:
https://github.com/SCratORS/Everchanging/blob/main/java/com/scrat/everchanging/EverchangingRender.java#L188
https://github.com/SCratORS/Everchanging/blob/main/java/com/scrat/everchanging/BackgroundScene.java#L22
https://github.com/SCratORS/Everchanging/blob/main/java/com/scrat/everchanging/FireWork.java#L38
https://github.com/SCratORS/Everchanging/blob/main/java/com/scrat/everchanging/ButterFlie.java#L1030
https://github.com/SCratORS/Everchanging/blob/main/java/com/scrat/everchanging/Dandelion.java#L270
...
the list is not exhaustive.

[Doctoror]

Fixed calendar commit needs merging after revert.