I tried but didn't work...this is what I get -
"$snap.vm`t([Math]::Round($snap.SizeGB))`t($snap.Created -replace $retime)"|out-file $outfile
Output
20121001.vm ([Math]::Round(20121001.SizeGB)) (20121001.Created -replace \d{1,2}:\d{1,2}:\d{1,2}.*?$)