title: How can I specify the latest time of day with DateTime
body: <p>I am using a <code>System.DateTime</code> object to allow a user to select a date range. The user is only able to select a date (not time) using a third party calendar so I will need to automatically specify the time of day it should use (ie: 00:00:00 or 23:59:59) after the date is chosen.</p>
  
  <p>How can I specify the time after the date is already stored as a DateTime object by the calendar selector? I could use the <code>AddHours, AddMinutes, AddSeconds</code> methods but those are relative to the current time which may not be 00:00:00.</p>
  
  <p>The <code>startDate</code> will need to have a time of 00:00:00 and <code>endDate</code> have a time of 23:59:59 to account for the entire days.</p>