This article explains the Time Selector block that can be added as a block to design an app.
Click on the block and start editing on the panel that appears on the right side.
This is what appears as the name of the input block to the end-user.
This is the text that goes below the input block to help the user.
If you want the users to input the current time, the system can pre-fill it for you. Tick on the option "Default to current time" for this.
By default, time editing is allowed for the user. If you want the users to not modify the current time, untick this option. Make sure you have ticked the current time option described above.
Tick this option if you want the user to compulsorily fill the time.
Can I find the difference between two time inputs?
Yes, you can add a formula block and subtract the two variables generated against each time input. Learn more about the formula block here - https://clappia.com/help/using-formula-block/
What will be the timezone of the input?
Since the user is providing input without any timezone, it should be assumed that the person has filled his/her timezone. In case the timezone is a strict requirement because your users are in different zones, you should add a dropdown block with all possible times zones for the users to select.