bug in cal(1)

[guy at gorodish.UUCP]

	> Here's a calendar not to use:
	> 
	> % /usr/bin/cal 1 87
	>    January 87
	>  S  M Tu  W Th  F  S
	>     1  2  3  4  5  6
	>  7  8  9 10 11 12 13
	> 14 15 16 17 18 19 20
	> 21 22 23 24 25 26 27
	> 28 29 30 31

Is that not the correct calendar for January in the year 87 A.D.?  What
should the calendar for that year be?