Im getting the exact same thing but with Simply Enterprise 2010 that ive been using for 9 years. 

I hope we get a suggestion to resolve this by some expert.

The answer has been posted several times on this forum.

Change your short and long date formats in Simply Accounting/Sage 50 for years prior to 2019 (2018 and earlier), to four digit years.

Kisses and Hugs for Richard!! Seriously Richard thank you for your time. I am a one man show and this (book keeping and accounting) is not my forte as I am a Truck Mechanic that know enough to make me dangerous. Arifa I hope this fixed you as well. Until next time thanks again.

Thanks Richard.  I got this email from Sage 50 Canada Support Team, which resolved the problem I had.

This is a known issue with all versions of Sage prior to 2019, it has been corrected in our latest versions of the software.

You can contact our sales team to upgrade the software or there is a workaround in your version. You will need to change the date format in the company settings to be a 4 digit year instead of a 2 digit year (yyyy instead of yy).