Timestamp fields indicate when an event happens. It is a type of Subject and controls how you want business metrics (measures) grouped in a report. When designing a report, you can toggle between Subjects and Time in the Select Grouping dialog box.

Display name Description Keys Tags
Interval Date Whole date, should NOT be used on the "FILTERS" panel Date  
Interval Time Used on the "FILTERS" panel as filters, such as date, month, year, etc (15/30-minute Period which is also the smallest granularity of data available for historical stats. ) timestamp  
Login Time The time when the agent logged in haglog_login_time  
Segment Start The time when the call segment started. segstart_utc Echi