When comparing WhatsApp vs Google Calendar, the Slant community recommends Google Calendar for most people. In the question“What are the best Material Design apps?” Google Calendar is ranked 6th while WhatsApp is ranked 34th. The most important reason people chose Google Calendar is:
The app leverages Google Maps when adding location for an event by offering suggestions as well as offers opening Maps to help get directions to an event via shortcut on a reminder notification.
Specs
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Pros
Pro Straightforward interface
The interface is very simple, fast and easy to use. You can start using it as soon as the app has been downloaded - it does not require setting anything up or registering. You can communicate with anyone in your contacts list that also uses WhatsApp. Includes useful features like seeing when a contact is currently available or typing.
Pro Widely used
WhatsApp reported 1.5 billion users in 2018. Your friends are most likely already using WhatsApp, so it's easy to get setup.
Pro Effortlessly builds your contacts by using your phone number as identification
WhatsApp will automatically find all of your contacts currently using Whatsapp and add them to your contacts. This makes it really easy to setup and given that it's the most popular messaging app it's likely that a lot of your contacts are already using it.
Pro Message mirroring on web app
WhatsApp can be used from the desktop via Chrome, Firefox and Opera browsers. Accessing it requires using the Android app to scan the QR code that's presented on web.whatsapp.com.
Pro Signal protocol
Whatsapp uses the state-of-the-art Signal protocol that ensure strong end-to-end encryption.
Pro One-on-one texts can be encrypted
WhatsApp has implemented end to end encryption for messages sent on it's service. Even WhatsApp has no way to read a users messages.
Pro Integrates with Google Maps for directions
The app leverages Google Maps when adding location for an event by offering suggestions as well as offers opening Maps to help get directions to an event via shortcut on a reminder notification.
Pro Comes pre-installed on most Android devices
Google Calendar is a free Android calendar app without ads that comes already installed on Android devices that have stock support for Google Services.
Pro Clean design with 5 different views including an excellent schedule view
Google Calendar has a monochrome base design that's accented with colored-coded events and image banners that separate months in schedule view.
The app has 5 different views - schedule, day, 3-day, week and month.
Day, 3-day and week views split up the days horizontally and hours vertically. Month view lays out all days in a grid and displays up to 3 events in a day.
Schedule view displays an agenda view that allows browsing all events by swiping vertically. Additionally, the way events are displayed in the agenda view is context-aware. For example, adding an event called "gym" will display the event on a background with a dumbbell.
All views except for month view can be split horizontally to display a condensed month view at the top that can be navigated by swiping horizontally.
Events can be added from any view by clicking the red plus button that's available at the bottom-right corner of the screen.
Pro Offers creating events from e-mail messages based on content
Google Calendar integrates with e-mail for quickly creating events from e-mails that contain the word "meeting" or dates or times, or any other information about events or plans that it can understand.
Pro Can set on-screen and e-mail reminder notifications
Google calendar allows setting how many reminders are needed with each having the ability to set how long before the event the notification should remind and if it should be done via on-screen or e-mail notification.
Pro Integrates well with other Google services
Google Calendar is part of the Google ecosystem, it integrates with services like Google Now for creating events, Google Maps for directions and Gmail for pulling information about planned flights.
Pro Color-coding for events and calendars
The app will color-code different calendars in different colors as well as allow selecting a different color for each event.
Pro Straightforward event creation with autocomplete
All views have an option of adding a new event by tapping the plus sign at the lower right corner of the screen. This opens up a form and allows the user to add a location, start/end times, guests, description, color-code as well as choosing if it's an all day event, how often it repeats, how many and what kind of reminders are needed and setting the users availability and privacy settings.
Pro Awesome flairs / images view inside the agenda view / event page
Whenever you enter agenda / event title with the keywords (when available), the event will show up interesting flairs whenever the keyword inside the agenda / title you typed matches the flairs that are available inside the system, examples such as haircut, cycling, swimming, coffee, movie etc.
Pro Allows subscribing to public calendars through web client
Through the Google Calendar's web client, it is possible to subscribe to any public calendar. Google also maintains a list of public calendars for various sports events and holidays in different countries and for different religions.
Pro Supports non-Google calendars (requires accessing web client)
Google Calendar can be integrated with any calendar that support iCalendar format, including Exchange and iCloud, via URL, but it has to be done using the web client.
Pro Lots of third-party widgets
Google Calendar comes with a home screen widget, and there are also many third party widgets developed for this calendar app.
Pro Advanced functionality available through IFTTT
IFTTT offers over 198 channels to plug into the users Google Calendar.
Cons
Con Shares meta data with Facebook
WhatsApp shares your messaging meta data with Facebook if you do not opt-out in the settings. If you use the same phone number for WhatsApp and Facebook, the profiles can easily be linked.
See https://www.whatsapp.com/faq/en/general/26000016
Con Tied to carrier phone number
WhatsApp cannot be used by people without a smart phone with an active cell plan. If your phone is lost or damaged, or if your phone number changes, you cannot get messages sent by friends without them updating your phone number. You cannot send message to them until you are able to get SMS messages at your phone number.

Con Proprietary
Not open source.
Con Hard to migrate history cross platform
Migrating your chat history from Android to iOS or the other way around is not so simple. In some cases it requires a 3rd party app and in some the only way is to migrate specific chats one by one.
Con Web interface uses message mirroring
To use your computer to send messages your phone must be on with a consistent data connection.
Con Single device
You cannot use the same WhatsApp account on multiple devices (e.g. a tablet, a PC and a cellphone). The account is tied to the device with the specific cellphone number. Chat history is deleted when you sign in to a new account, unless you have created a backup.
Con No cloud sync
Messages are not stored on WhatsApp server for privacy and security reasons.
Con Limitation on shareable file sizes
WhatsApp now allows users to share files of any type, but there is still a 16 MB size limit.
Con No vertical scroll
Like iOS and outlook for Android.
Con Privacy concerns
Google integrate all their services to connect and mine information on an individual to better profile and target advertising.
Con Google tasks do not show on Google Calendar
You can create tasks in your desktop Google Calendar but they will not sync nor show up in your android Google Calendar
Con Setting up non-Google calendars requires accessing web client
There is no ability in the Android app to access other calendars. This limits the usefulness for people that use more than one calendar, such as OSX and iOS users.
Con No weather forecast
The Android app version of Google Calendar does not show any weather forcast information, even if it is added as an extra calendar in the web application. Being that weather is tied into Google Now, the absence is surprising.
Con Setting up CalDAV or iCAL from other sources is not working or not working well
A lot of people share events between different sources: professional, private, family or friends.
Not everybody is on Google and of course a lot of corporations.
Con Month view shows limited information about the event
Month view does not show how many events there are in each given day or color-code them in any way, only informs of their existence.
Con Does not work well with Apple / iCloud Calendar
Apple and Google calendars have syncing issues, which is annoying if you want to have shared calendars with friends / family.
Con Some recurrence options not available
If you want to add a recurring event based on quirky (but normal) calendar rules, it's not supported by Google Calendar. For example, if you set up a financial calendar in Google Calendar and an event falls on a weekend or bank holiday, Google Calendar cannot schedule the occurrence properly. Worse yet, if you submit those calendar occurences via VEVENT details, Google Calendar displays different information if you use the mobile calendar vs. the desktop web calendar.
Con Once you create a event on a Calendar, you can't move to a different Calendar
Con Horizontal Scroll
Does not vertically scroll like ios calendars on outlook calendar.
Con Slow syncing of external calendars
Google Calendar is known to sync external calendars very slowly, takes hours if not a full day before the updated events are reflected.
Con No natural language input support
The Android app has no natural language input support, while it's available using the web client and in a limited capacity using Google Now.
Con Weak default view
Even if month is set as default view, as soon as you touch a day or an event, you have to carefully select twice to get back to month view.
Con Time zone is incorrect no matter what's done
Con Timezone for Moscow is incorrect
Timezone for Moscow is 1 hour off. This makes the calendar unusable in Russia.
