To separate two numbers.
January 31, 1915.
By the end of 1914, 7062 had been built.
22.

To indicate an ellipsis.
Subscription for the course, one dollar.
Exceptions to this rule are made in very brief sentences, especially in advertisements: Tickets 25 cents.

Price one dollar.
The foregoing rules for the use of the comma have been compiled from those given by a considerable number of authorities.

Further examination of authorities would probably have added to the number and to the complexity of these rules.

No two sets of rules which have come under the writer's observation are alike.