Tickets in RT have several date fields:
Starts and Due dates work like expected (planned) time boundaries, while Started and Resolved are set after things happen. How this works is described below.
This is the first date that is set during creation of a ticket and cannot be changed using the UI.
Starts date is used to indicate the time when staff expects to begin to work on the current ticket. Editable and optional.
RT uses Started date to indicate the time when a user actually begins work on the ticket. This date is set to "now" automatically when status of the ticket is changed from 'new' to any other value. So if the server is configured to 'auto open' tickets on correspond, then it's set on correspond. However, if somebody opens it before any correspondence then it's also set.
Try next tests:
- create a ticket, click the open action and look on the dates box
- create a ticket, click the resolve action and look on the dates box
Starts vs. Started
There are no restrictions on these dates, so work on ticket could begin (started) earlier than it was expected (starts) or vice versa.
Due date defines a deadline for the ticket. You can implement SLA or projects' deadlines using this field. Editable and optional.
Told (Last Contact)
Is set when inbound user replies to a ticket or can be set manually. Last time that requestors were notified by someone.
This date is set automatically to now when ticket is changed in any way.
Users who have the correct rights can set Starts, Started, Told and Due dates. These dates and others can be set automatically as described above.
To change a date, open a ticket and click on title of the 'Dates' box or 'Dates' subtab in the menu. From this page, you can adjust dates of the ticket.
To change any of these dates, type the new date in the text box and click the Submit button. In recent versions you can use calendar popup to pick a date.
NOTE: Acceptable date formats such as mm/dd/yy or dd/mm/yyyy vary by organization and country. If you're not sure, ask an administrator how to enter dates. Administrators can consult with manual for a date parsing perl module.
Dates can also be changed from the bulk update option. See ManualTicketsBulkUpdate.
Unset (delete) Date
To delete date or clear date, simply enter the number 0 in the date field and save. This will change the date field to "not set". This totally sounds like a bug and should be fixed.
Searching by dates
It's possible to search using not only absolute dates like '2009-11-30', but also relative dates like '7 days ago'. This is described in details ManualSearchOnDates.