Additionally, WhatsApp is testing a new feature that allows it to provide these facts when you click the plus symbol at the bottom of the screen.
According to WAbetainfo's most recent article this week, Android users running version 2.24.9.14 are able to beta test the new functionality. Essentially, the messaging app is adding a new option to its design called Recently online. This tab is located directly above the part where you can view the names of all of your WhatsApp connections.