You completely forgot about the quotes surrounding the strings.
Not to mention that representing the date in that way is completely silly and inefficient.
It's just an example, there was no question of anyone rating silly or not. The question was why an extra zero appears in the value. Also, if a value like 23.23 is added, the value will be stored as 23.0.0.23.
Even if you keep the value in quotes, yes, it will not be modified. But if you change the value of the variable through the winbox interface, the null will still be added. And I would like to understand why it works like that.