I’m feeling very bad to inform you that the examination of gate has already held. This exam was conducted on 12th Feb, 2017. So, neither you can apply for gate exam nor appear in its exam.
You can apply next time. There is no any age limit in this particular. Only criteria is that you have to have your degree.
Don’t feel disheartened and try for next time.
Take a look on this year question papers and prepare yourself.
All the best.