BibTeX, biblatex and biber ⇒ Removing period after year

[fr33sh1]

I have a problem with custom bibliography style.
I need to remove "." that occurs after year (it would be great If it could be replaced with a comma):

Melnikov, I. The arctic sea ice ecosystem. Gordon and Breach Science Publishers, 1997. 204 ss.

This is the Function that defines the periods used after blocks (red colour is what I added):

Code: Select all

FUNCTION {output.nonnull}
{ 's :=
  output.state mid.sentence =
    { add.period$ " " * write$ }
    { output.state after.block =
        { add.period$ write$
          newline$
          "\newblock " write$
        }
        { output.state before.all =
            'write$
            { add.period$ " " * write$ }
          if$
        }
      if$
      mid.sentence 'output.state :=
    }
  if$
  s
}