changelog: Use consistent date format.
changelog: Use consistent date format.

andersk/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip,rht/zulip,andersk/zulip,andersk/zulip,zulip/zulip