Google Calendar is a wonderful tool. While many people may know that you can import pre-made calendars with lists of various holidays in them, there's a lot more cool stuff you can do with the service.
Embed Weather Forecasts
One of the neatest features built right in to Google Calendar is the ability to add weather forecasts to your events. To add this, go to Settings on the web and under the General tab, enter a location you want to get the weather for. Directly below that, choose either Celsius or Fahrenheit (please, not Fahrenheit) from "Show weather based on my location". Click Save and the next few days on your calendar will have a brief weather forecast in the upper right corner of each day.
Automatically Add Your Travel Itinerary
TripIt is one of our favourite travel services already. It scans your emails and adds any travel itineraries or reservations to its own app. That's all well and good, but if you'd like to also include those events in your Google Calendar, TripIt can do that, too. Between this, Google Now, and Gmail, you'll always be notified of everything you're doing on holiday.
Share Your Facebook Events With Google
One of the most useful tools in Facebook is the ability to coordinate events with nearly everyone you know. If you want to get your Facebook events in your Google Calendar, you can import them directly. In Facebook, head to your Events page, click the Settings drop down and select Export. Here you can right-click on either a link to your friends birthdays or upcoming events, copy the URL, and add that feed to your Google Calendar.
Save Foursqure Check-Ins To A Calendar
Foursqure is neat for saving your location (or getting free Wi-Fi passwords). Adding your locations to a Google Calendar gives you an easy way to backtrack to that place you went to two weeks ago. This IFTTT recipe will automatically add the location of your Foursquare check-ins to its own calendar for easy review later.
Create An Event To Remind You About Starred Emails
Starred emails in Gmail are fantastic for reminding yourself to deal with things later. If you're still likely to forget, however, you can be reminded with calendar events. This IFTTT recipe will create an event at a time you specify to remind you to check any email you star in Gmail. You can also use this recipe to create any event you choose using an email. While this might not be the most useful if you already have a calendar app for yourself, you can use customised search terms to allow others to add events to your calendar via this method as well.
Find Out Today's Current Stardate
Yes, this is real. Without installing a thing, Google Calendar has the ability to tell you what today's current Stardate is in the Star Trek universe. Just like the sports and holiday calendars, click the dropdown box next to "Other Calendars" on the web and choose "Browse Interesting Calendars". Under "More" you'll find Stardates near the bottom. This will not help you keep a captain's log, however. Maybe try Google Drive.