我用EXCEL 解决了。但是不知道用SAS如何解决。

遇到同样的问题，想知道您后来问题解决了没有？如何解决？

可以使用proc expand：
The EXPAND procedure converts time series from one sampling interval or frequency to another and interpolates missing values in time series. A wide array of data transformations is also supported. Using PROC EXPAND, you can collapse time series data from higher frequency intervals to lower frequency intervals, or expand data from lower frequency intervals to higher frequency intervals. For example, quarterly values can be aggregated to produce an annual series, or quarterly estimates can be interpolated from an annual series.

详见：https://support.sas.com/document ... _expand_sect001.htm
How do I create  time series variables using proc expand? | SAS FAQ (ucla.edu) 之
https://stats.idre.ucla.edu/sas/faq/how-do-i-create-time-series-variables-using-proc-expand/