We have found one software suitable in our database for this conversion.
When you import your .pst file to Outlook, you can export the calendar data to several different formats, including iCalendar ICS format, which will essentially achieve pst to ics conversion.
You can do that by accessing calendar in Outlook and then selecting the File ► Import/Export function to save your calendar data as.ics file.
PST
A pst file extension is used for storage file format of Microsoft Outlook. PST file contains stored emails, calendars, contacts in one single file.
ICS
Files with ics extension are calendar data in exchange format which is widely accepted in many personal information managers and e-mail clients such as Microsoft Outlook, or Apple iCal. It is an universal format for transporting calendar data and events from one program to another.