This article teaches you how to find out the date and time someone last used WhatsApp on their device.
Step
Method 1 of 2: iPhone

Step 1. Open WhatsApp
The app is green with a white phone icon inside a text bubble.

Step 2. Tap Chats
This button is represented by the icon of two text bubbles at the bottom of the screen.
If you are in a conversation, press the arrow Back first at the top-left of the screen.

Step 3. Tap a conversation
Select one conversation with one individual.
Group conversations do not display “last seen” or “last seen” information

Step 4. Look at the date and time
After the conversation loads, “last seen (date) at (time)” or “last seen (date) at (time)” will appear under the contact name at the top of the screen. This is the date and time your contact last accessed WhatsApp on their device.
If the word "Online" appears below the contact's name, it means that the WhatsApp application is open on their device
Method 2 of 2: Android

Step 1. Open WhatsApp
The app is green with a white phone icon inside a text bubble.

Step 2. Tap Chats or Chats
If you are in a conversation, tap the arrow Back first at the top-left of the screen.

Step 3. Select a contact
Tap a contact name.

Step 4. Look at the date and time
After the conversation loads, “last seen (date) at (time)” or “last seen (date) at (time)” will appear under the contact name at the top of the screen. This is the date and time your contact last accessed WhatsApp on their device.