after +过去时间是一般过去时态的杯志词，中文意思是“一九九零年以后”

例如，一九九零年以后，他只身一人来到杭州打工谋生活，到现在已经有三十多年了。

For example， after 1990， he came to Hangzhou alone to work for a living， and it has been more than 30 years now.