Sat Sri Akal
Here are the reasons why Paul Singh Purewal of Edmonton,Canada researched and presented his findings to convince SGPC to go with Solar calendar rather than the Lunar calendar.
(1). Every year some pundit had to be called by the SGPC so he could tell us when our Gurpurabs were.
(2). If we didn't fix our dates now to solar calendar then in few hundred years the dates were going to be too out from our cultural aspect and spritual aspect.
This was the time to change and keep our dates.
(3) This is a 99 year (1499-1599-1699-1799-1899-1999) and something good always happens in 99!
This was what was told by Mr> Purewal and many other reasons in articles in Journal of Sikh Studies.