Correct ERA5 timestamp convention (#2773)

* Correct era5 timestamp convention

* Add Whatsnew

* Update whatsnew based on reviewer feedback

Author: AdamRJensen

docs/sphinx/source/whatsnew/v0.15.2.rst

@@ -22,6 +22,10 @@ Bug fixes
   introduced in v0.15.1 (:pull:`2702`) that caused a broadcasting
   ``ValueError`` when ``tracker_theta`` was a 2-D (or higher rank) array.
   (:issue:`2747`, :pull:`2749`)
+* Document that timestamps returned by :py:func:`~pvlib.iotools.get_era5`
+  represent the end of the averaging interval, consistent with ERA5
+  conventions. (:issue:`2772`, :pull:`2773`)
+
 
 Enhancements
 ~~~~~~~~~~~~

pvlib/iotools/era5.py

@@ -102,7 +102,7 @@ def get_era5(latitude, longitude, start, end, variables, api_key,
     Returns
     -------
     data : pd.DataFrame
-        Time series data. The index corresponds to the start of the interval.
+        Time series data. The index corresponds to the end of the interval.
     meta : dict
         Metadata.