diff --git a/bin/weewx/units.py b/bin/weewx/units.py
index 8a05270f..6e8e7fcd 100644
--- a/bin/weewx/units.py
+++ b/bin/weewx/units.py
@@ -1286,14 +1286,30 @@ class SeriesHelper(tuple):
     def data(self):
         return self[2]
 
-    def json(self, order_by='row'):
+    def json(self, order_by='row', time_series='both'):
         import json
 
+        time_series = time_series.lower()
+        if time_series not in ['both', 'start', 'stop']:
+            raise ValueError("Unknown option '%s' for which time series to include" % time_series)
+
         if order_by == 'row':
-            json_data = [[start_.raw, stop_.raw, data_.raw]
-                         for start_, stop_, data_ in zip(self.start, self.stop, self.data)]
+            if time_series == 'both':
+                json_data = [[start_.raw, stop_.raw, data_.raw]
+                             for start_, stop_, data_ in zip(self.start, self.stop, self.data)]
+            elif time_series == 'start':
+                json_data = [[start_.raw, data_.raw]
+                             for start_, data_ in zip(self.start, self.data)]
+            else:
+                json_data = [[stop_.raw, data_.raw]
+                             for stop_, data_ in zip(self.stop, self.data)]
         elif order_by == 'column':
-            json_data = [self.start.raw, self.stop.raw, self.data.raw]
+            if time_series == 'both':
+                json_data = [self.start.raw, self.stop.raw, self.data.raw]
+            elif time_series == 'start':
+                json_data = [self.start.raw, self.data.raw]
+            else:
+                json_data = [self.stop.raw, self.data.raw]
         else:
             raise ValueError('Unknown order by option %s' % order_by)
 
diff --git a/docs/series_tags.md b/docs/series_tags.md
index 3e1710f2..d536f999 100644
--- a/docs/series_tags.md
+++ b/docs/series_tags.md
@@ -14,6 +14,18 @@ include the keyword `series`:
 $period($data_binding=binding_name, $optional_ago=delta).obstype.series[.optional_unit_conversion][.optional_formatting]
 ```
 
+## JSON formatting
+By adding the suffix `.json()` to the tag, the results will be formatted as JSON. This option has
+two optional parameters, `order_by` and `time_series`:
+```
+.json(order_by=['row'|'column'], time_series=['start'|'stop'|'both'])
+```
+`order_by`: The returned JSON can either be organized by rows, or by columns. The default is `row`.
+
+`time_series`: This option controls which series are emitted for time. Option `start` selects the
+start of each aggregation interval. Option `stop` selects the end of each interval. Option `both`
+causes both to be emitted.
+
 ## Series with no aggregation
 Here's an example of asking for a series with the temperature for all records in the day. We will
 display it with an HTML `<pre>` tag so that the embedded newlines work.