diff --git a/saqc/funcs/functions.py b/saqc/funcs/functions.py
index 18ab8bece3bd7b73b97a268057833d62e6996132..c56303fa7fedfe4b247fe2db5b11102545f5b9f8 100644
--- a/saqc/funcs/functions.py
+++ b/saqc/funcs/functions.py
@@ -233,8 +233,8 @@ def flagSesonalRange(
 
     data, flagger = proc_fork(data, field, flagger, suffix="_masked")
     data, flagger = modelling_mask(data, field + "_masked", flagger, mode='seasonal',
-                                   season_start=str(startmonth).zfill(2) + '-' + str(startday).zfill(2) + 'T00:00:00',
-                                   season_end=str(endmonth).zfill(2) + '-' + str(endday).zfill(2) + 'T00:00:00',
+                                   season_start=f"{startmonth:02}-{startday:02}T00:00:00",
+                                   season_end=f"{endmonth:02}-{endday:02}T00:00:00",
                                    inclusive_selection='season')
     data, flagger = flagRange(data, field + "_masked", flagger, min=min, max=max, **kwargs)
     data, flagger = proc_projectFlags(data, field, flagger, method='match', source=field + "_masked")