Remove unused clearsky._is_leap_year (closes #2768) (#2813)

* Remove unused clearsky._is_leap_year (closes #2768)

* Add contributor entry to whatsnew

* Address review comments: fix pull number and contributor entry

* Address review comments: fix pull number, contributor entry, restore blank lines

Author: dgowdaan-cmyk

docs/sphinx/source/whatsnew/v0.15.3.rst

@@ -42,6 +42,7 @@ Requirements
 
 Maintenance
 ~~~~~~~~~~~
+* Removed unused internal function ``clearsky._is_leap_year`` (:issue:`2768`, :pull:`2813`)
 * Fix documentation builds on runner images lacking link-type timezones. (:issue:`2795`, :pull:`2809`)
 
 
@@ -50,3 +51,4 @@ Contributors
 * Eesh Saxena (:ghuser:`eeshsaxena`)
 * Karl Hill (:ghuser:`karlhillx`)
 * Yonry Zhu (:ghuser:`yonryzhu`)
+* Darshan Gowda (:ghuser:`dgowdaan-cmyk`)

pvlib/clearsky.py

@@ -220,22 +220,6 @@ def lookup_linke_turbidity(time, latitude, longitude, filepath=None,
     return linke_turbidity
 
 
-def _is_leap_year(year):
-    """Determine if a year is leap year.
-
-    Parameters
-    ----------
-    year : numeric
-
-    Returns
-    -------
-    isleap : array of bools
-    """
-    isleap = ((np.mod(year, 4) == 0) &
-              ((np.mod(year, 100) != 0) | (np.mod(year, 400) == 0)))
-    return isleap
-
-
 def _interpolate_turbidity(lts, time):
     """
     Interpolated monthly Linke turbidity onto daily values.