To set up email reminders for approvers and remind them to approve the user time, follow these steps:
1. Create a Scheduler:
Go to Setup and search for Scheduled Jobs.
Click the Schedule Apex button in the All Scheduled Jobs section.
Enter the Job Name (e.g., "Daily Email Reminders").
Select Daily Email Reminders in the Apex Class dropdown.
Set the frequency and preferred time for the email reminders.
Click Save to schedule the job.
Set Up the Flag:
Go to the TimeTracker Flags object and search for "Remind approvers after days" and click it.
In the Text Value, enter Pending Approval, and days, e.g: Pending Approval,1,2,4,5.
This reminds the approver if the approver has not approved the time details. The approver will get an reminder email on every 1, 2, 4 and 5 days
Click Save to activate the flag settings.

Create an Email Template:
Go to Setup and search for Classic Email Templates.
Click New Template to create a new email template.
Design the content of the email, reminding approvers to approve the time details, (HTML Template)
Include any specific instructions or links relevant to the approval process.
Save the template.

Notification Process:
Once the scheduler is enabled, the flag is set, and the email template is created, approvers will automatically receive reminder emails if they have not approved their time details according to the specified schedule.