diff --git a/pandas/_libs/tslibs/timedeltas.pyx b/pandas/_libs/tslibs/timedeltas.pyx
index 2be2338253937..5bc3694cf8dad 100644
--- a/pandas/_libs/tslibs/timedeltas.pyx
+++ b/pandas/_libs/tslibs/timedeltas.pyx
@@ -584,7 +584,7 @@ cdef inline int64_t parse_iso_format_string(str ts) except? -1:
         bint have_dot = 0, have_value = 0, neg = 0
         list number = [], unit = []
 
-    err_msg = "Invalid ISO 8601 Duration format - {}".format(ts)
+    err_msg = f"Invalid ISO 8601 Duration format - {ts}"
 
     for c in ts:
         # number (ascii codes)
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index 12d44413e1350..9fd62e5e25c54 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -191,10 +191,10 @@ def integer_op_not_supported(obj):
 
     # GH#30886 using an fstring raises SystemError
     int_addsub_msg = (
-        "Addition/subtraction of integers and integer-arrays with {cls} is "
+        f"Addition/subtraction of integers and integer-arrays with {cls} is "
         "no longer supported.  Instead of adding/subtracting `n`, "
         "use `n * obj.freq`"
-    ).format(cls=cls)
+    )
     return TypeError(int_addsub_msg)