[lifeisstillgood]

In every language I know there is a set if conventions around Null values, not set values, true, false and zero

We have only had the concept of zero for a thousand years and null for about fifty. Expecting there to be a common way of handling this in all domains and industries is a bit much and expecting it to be handled the way the OP prefers is highly unlikely (although I do agree with their opinion)

If the convention in accountancy is BLANK == 0 then that's their convention. Implement it using a single method that's nice and easy to instrument and discover for later on, perhaps raising warnings out to the reports produced.

Leave the worrying over not set values for when Unicode and UTC handling in excel is brought up :-)

[flynnieous]

The concept of zero is at least 3,700 years old. The Egyptians used it in their accounting. See http://en.wikipedia.org/wiki/Egyptian_numerals#Zero_and_nega...

[bitL]

Null is probably also much older: https://en.wikipedia.org/wiki/Mu_%28negative%29