As per the situation described by you it is very clear that the employee code of conduct is not very clearly set up in the organization you are working at.
For this you need to come up with some strict rules and regulations to put an end to the employees leaving abruptly. Also, as an HR you need to find out whats making them leave this way? Is there something wrong with the present company policies, which is most likely the case here. And in this case you need to give suggestions for improvement to your superiors to avoid such attrition.
As far as the date of leaving in the experience letter is concerned it should always be the last working day of the employee which in this case has no connection with the handover period. You should mention the date when the employee last came to work before leaving. Hand over of responsibilities is just something they are doing in order to get the full and final formalities done.
Hope this helps
Sounds stumpy when HR has to face such an earnest situation on how to releive the employees. In simpe words such employees are said to be "Absconded employees".
Employee exit interview is usually conducted after both voluntary and involuntary separations. The meeting provides a forum for the departing party to voice their concerns and understand the reasons behind their termination (in your case, an absconded employee) while giving the company valuable feedback for reevaluating its policies and practices. Keep a track of all the certainities and discuss the same with the management.
As an experience letter carries the utmost value for any employee for his tenure over a period that he was engaged with the employer. You should always make sure that the fact is entailed in the letter. You might also want to say, the employee's last date of working and "No show" and "NP not given" which also reputes on company's perspective if the next employer seeks BGV.
Absentism causes due to two or more alternative places for the employee to discharge his functions, he becomes high prone to abscond. The employee feels less motivated to go to work, the fact that there is an alternative work environment could lift his spirits and prompt him to attend to his duties because of the change in surroundings. That is the reason of "Attrition". Talk to the Departments, make appropriate motivational levels of practise at work place, competitive and commendable high spiirts will haul up the space of enthusiaism at work.
P.S. An HR should be able to initiate such things for uplifting the organizational eminence.
I would like to thank you for your valuable time spent on giving solution to my issue. I forgot to tell you that, it is a family run business, wherein with my experience in change management skill, am unable to make any changes (FYI I was successful in two of my previous careers in full change management).
Also this civil construction industry also is a higly unorganized one, still I'll make my efforts in line with your valuable suggestions.