Hi, I'm using the spreadsheet control and i'm having an issue with date columns.

When I enter a valid date, it works fine.

but when I enter an empty date (clicking delete on date column, or emptying out the contents)

the date gets stored as "new Date(0,0,-1)" ["Sat Dec 30 1899 00:00:00 GMT+1130 (New Zealand Daylight Time)" in my local time]

obviously, this is incorrect, and it should store the value as NULL.

it happens regardless of whether the schema/model has nullable=true.

If I manually modify the dataItem via JS, it stores it correctly as null. 

I have a dojo demo set up which replicates the issue.

https://dojo.telerik.com/oFowivUN

Steps:

1. select the ItemDate column of the first row in the spreadsheet
2. type in a valid date (e.g. 1/1/2020)
3. Click View ItemDate button (It should show the correct date)
   
4. Select the ItemDate column and empty it out (e.g. click delete)
5. Click View ItemDate button. (it should now show the incorrect date!)

Doing some investigation into the kendo code, it seems to be caused by the serialToDate method of the spreadsheet.

Thanks