The main contest around year of Gaussian Curvature
Contests
All information, dates, appropriate for which exam and how to register is given below , scroll down to check.

GAMO & GJMO
GAMO(Gaussian Universal Standard Mathematical Olympiad) and GAMO(Gaussian Universal Standard Junior Mathematical Olympiad) are intended at the level of USAMO and USAJMO. The contest is followed by GIMO(Gaussian International Mathematical Olympiad) which is an IMO standard/level Contest.

GIMO
Gaussian International Mathematical Olympiad is a contest aimed at International Mathematical Olympiad Level and is the next stage og GAMO and GJMO.

MMO
An international yearly independent single stage contest aimed at IMO level and standard
Contests
You can check the contest of GC from above, there are helpful for several mathematical olympiads. Register means a contest whose registration is open, Pre-Register means the contest is not declared yet but you can pre-register.