Remove deprecation warning of the utcnow function

src/joseki/accessor.py

@@ -423,7 +423,7 @@ def rescale(
             raise ValueError("Cannot rescale") from e
 
         # update history attribute
-        now = datetime.datetime.utcnow().replace(microsecond=0).isoformat()
+        now = datetime.datetime.now(datetime.UTC).replace(microsecond=0).isoformat()
         for m in factors.keys():
             ds.attrs["history"] += (
                 f"\n{now} - rescaled {m}'s mole fraction using a scaling "
@@ -471,7 +471,7 @@ def drop_molecules(self, molecules: t.List[str]) -> xr.Dataset:
         ds = self._obj
 
         # update history attribute
-        now = datetime.datetime.utcnow().replace(microsecond=0).isoformat()
+        now = datetime.datetime.now(datetime.UTC).replace(microsecond=0).isoformat()
 
         ds.attrs["history"] += (
             f"\n{now} - dropped mole fraction data for molecules "

src/joseki/core.py

@@ -162,7 +162,7 @@ def merge(
     )
 
     # update attributes
-    now = datetime.datetime.utcnow().replace(microsecond=0).isoformat()
+    now = datetime.datetime.now(datetime.UTC).replace(microsecond=0).isoformat()
 
     institutions = set([ds.attrs["institution"] for ds in datasets])
     sources = set([ds.attrs["source"] for ds in datasets])

src/joseki/profiles/util.py

@@ -16,7 +16,7 @@ def utcnow() -> str:
     Returns:
         ISO 8601 formatted UTC timestamp.
     """
-    return datetime.datetime.utcnow().replace(microsecond=0).isoformat()
+    return datetime.datetime.now(datetime.UTC).replace(microsecond=0).isoformat()
 
 
 def number_density(p: pint.Quantity, t: pint.Quantity) -> pint.Quantity: