is converted to,2013-03-1 strftime (time, "%Y-%m-%W").
and strptime (strftime (time, "%Y-%m-%W"), "%Y-%m-%W"), not converted.
I want to know how to solve.
In case you're trying to "round down" a timestamp to the start of the week you should do this instead:
eval my_time = relative_time(_time, "@w1")
If you consider Sunday to be the start of the week you can use @w or @w0.