This bug was fixed in the package gnome-calendar - 3.19.90-0ubuntu1
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gnome-calendar (3.19.90-0ubuntu1) xenial; urgency=medium
* New upstream version (ffe lp: #1551877)
- dynamically change colors (lp: #1551766) or names (lp: #1551763)
* debian/patches/use_gtk_318.patch:
** Attachment removed: "debdiff for the update"
https://bugs.launchpad.net/ubuntu/+source/gnome-calendar/+bug/1551877/+attachment/4585778/+files/gnome-calendar.diff
** Patch added: "debdiff for the update"
https://bugs.launchpad.net/ubuntu/+source/gnome-calendar/+bug/1551877/+attachment/45