The heading of a friendly letter should contain the return address (usually two lines) followed by a third line with the date.
In a friendly letter the heading is always indented to the middle of the page.
If the correspondents are familiar enough and the recipient knows the writer's address, or if the stationery is imprinted with the return address, then the return address may be omitted. (Although another reason for the return address is a backup in case the envelope gets damaged...)
Always include the date.
Example:123 Main St.
West Newfield CT 06123
December 14, 2002
(Most authorities skip a line between the address and the date.)