Interviewer instructions
8.24. In which month and year did [the respondent] last work? (Q - 25).
Those who answered affirmatively to question 24, that is, those who have previously worked, should be asked the month and year of when they last worked.
[p. 108]
If the month corresponds to 1970, record the month abbreviating with the first three letters or the month's number and then write "70". If the month corresponds to a year previous to 1970, write only the year.