If you alter your device's date/time, will the Christmas event still be activated?
Solution 1:
Yes, you can manually set your device's date to get any of the season events to occur. This is mentioned on the wiki page for the Christmas event:
Hint: You can "activate" Christmas by setting your computer's or mobile's date to a day between December 15th and 31st.
The Seasonal event page lists all of the dates during which the various events are active.