i Register
In some senses, reckoner is marked as archaic. Watch for register when choosing this word.
noun
One who reckons.
“No. Not quite a month.—It is only four weeks to-morrow since I left Mansfield.” “You are a most accurate and honest reckoner. I should call that a month.”
middle-aged (-ajd), between youth and old age, variously reckoned to suit the reckoner
An accountant; one who computes or calculates.
An ordinator.