date picker: Use `dateFormat` which matches the field's expected format

4 jobs for master in 16 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Test
passed #110756
py27-django111

00:00:16

passed #110757
py36-django111

00:00:15

passed #110758
py36-django21

00:00:15

passed #110759
py36-django22

00:00:15