Dear community!
I am conducting a research on public opinion combined with different survey rounds, and I want to declare my dataset to be time-series. However, Stata doesn't allow to do this due repeated time values.
The key feature is that each survey has different respondents and different years, which common for respondents from particular survey. Thus I have something as follows:

year . idno.
2002 123
2002 124
2002 125
2004 126
2004 138
2006 185
2006 ...
2006 (id values are different)

Could you help me please with my issues to declare my dataset to be time-series?

Kinds regards,