@ Lavanya1981,
Good Afternoon.....!!!!!
You can get the details though EPFO Portal, Just Download "EMPLOYER E-SEWA FORM No. 23" for the year employee has resigned you will get the Exact Date of joining.
You may also get the details from their payslip, (if you have in house software where the date is maintained).
Other ways to maintain employee details are :
1) Create Employee date sheet (excel file) which contains Employee Name, Address, DOB, DOJ, Gender, Salary Account Number, PF account Number, ESIC account number etc.
2) You may also create personal file which contains, Resume, offer letter, Joining documents like: Photo ID proff, Address proof, Pan Card Xerox, Copy of Form - 2 (PF), Copy of Declaration Form (ESIC), Appointment, confirmation & Increment Letter Xerox, Agreement copy, Resignation Letter or any other relevant documents.
I hope this will help you as a fresher HR-Executive.
All the best.