Peter Hewkin, an ex-RAF officer from Worksop, was a regular visitor to the city while he studied a masters degree at the University of Sheffield.
He would usually park in Northumberland Road, Crookes, where he would pay 50p per hour for an on street bay with a maximum stay of four hours.
During a recent hospital visit he tried to park in the same road, but had to turn down a side street as there were no free spaces.
Quickly checking it wasn't a permit-holders only area, Mr Hewkin put £2 in the machine, expecting his ticket to run out at 6.15pm.
He came back to his car at about 5pm and was surprised to find a notice on his windscreen.
Confused, he checked his ticket and saw that it had expired at 4.15pm - or, as it was printed in 24-hour formet, 16.15. The sign on the street, meanwhile, was in 12-hour format.
Mr Hewkin then checked the machine where he bought his ticket and found that unlike Northumberland Road, the side street had a two hour maximum stay. His ticket confirmed that the machine had accepted over-payment of £1 - something he says those in the city centre do not do.
Mr Hewkin has begrudgingly paid his fine. But he is sure he is not the only driver to be confused by street-by-street and sign-by-sign differences.
"This is just not very good," he said. "If I got caught by it, I won't be the only one.
"Other people must have points to make about genuine misjudgements. I thought I had paid.
"I didn't realise it said that and it's just misleading."
Mr Hewkin said the use of the 12 or 24-hour clock was 'consistent in one place and inconsistent in another' - and a quick glance at his ticket had put the number 6 in his head.
He said it was the council's duty to make things as clear as possible.
"People normally make these mistakes unless you help them in some way not to make them," he said.
"Don't design it to be easy to get wrong. If you do that you are partly - if not largely - to blame for what happens."
Have you been caught out by inconsistent signs or tariffs? E-mail [email protected]