Clean up old datasets
Clean out old directories from crashed downloads
Check ds_str length

>>> time.strptime("20130713", "%Y%m%d%H")
time.struct_time(tm_year=2013, tm_mon=7, tm_mday=1, tm_hour=3,
                 tm_min=0, tm_sec=0, tm_wday=0, tm_yday=182,
                tm_isdst=-1)