Simple Date Rules For Copy Cats--AACR and RDA: Books

Date of production is a core element for resources issued in an unpublished form—RDA 2.7
Date of publication is a core element for published resources—RDA 2.8
Date of distribution is a core element for a resource in a published form if the date of publication is “not identified”—RDA 2.9
Copyright date is a core element if neither the date of publication nor the date of distribution is identified—RDA 2.11
Date of manufacture is a core element for a resource in a published form if the date of publication, the date of distribution, and the copyright date are all not identified—RDA 2.10

Supplied (inferred) dates are given as Arabic numbers, in square brackets, e.g., [2003].

For more instructions on recording a supplied (guessed) date, see (as appropriate):

AACR

1.4F1: For published items, give the date of publication, distribution, manufacture, or copyright as a year, using Arabic numbers, e.g., 2000.

Abbreviate a copyright symbol as 'c' (Copyright) or 'p' (Phonogram copyright)

RDA

1.8 and 1.7: Transcribe dates of publication, distribution, manufacture, or copyright “in the form in which they appear” e.g.:

Enter a copyright symbol as © or ℗; or, if you are unable to enter a copyright symbol, enter the word ‘copyright’ or ‘phonogram’ instead.

The LCPS for 2.8.6.6 is very useful for help with date decisions