Fixed sorting by date #1412

pkg/yqlib/doc/operators/datetime.md

@@ -60,7 +60,7 @@ a: 2001-12-15
 ## Format: get the day of the week
 Given a sample.yml file of:
 ```yaml
-a: 2001-12-15T02:59:43.1Z
+a: 2001-12-15
 ```
 then
 ```bash

pkg/yqlib/doc/operators/sort.md

@@ -135,6 +135,24 @@ will output
 - a: 100
 ```
 
+## Sort by custom date field
+Given a sample.yml file of:
+```yaml
+- a: 12-Jun-2011
+- a: 23-Dec-2010
+- a: 10-Aug-2011
+```
+then
+```bash
+yq 'with_dtf("02-Jan-2006"; sort_by(.a))' sample.yml
+```
+will output
+```yaml
+- a: 23-Dec-2010
+- a: 12-Jun-2011
+- a: 10-Aug-2011
+```
+
 ## Sort, nulls come first
 Given a sample.yml file of:
 ```yaml