4. Age
[Age] in years completed. For people younger than one year, write the number of months followed by the letter "M". For people younger than one month, write the letter "X"
For children who have not completed one year of life, the number of months completed, followed by the letter "M", is written down. E.g., for a child who was 2 months and 20 days old at the time of enumeration, the annotation in the fourth column would be "2M" which refers to the number of months completed, not counting of the number of days that have passed in the month.
For children who had not completed one month of life at the time of enumeration, an "X" is written down. It does not matter if the infant is 1 or 29 days old.
[p. 19]
Age is an extremely interesting piece of information and it should not, under any circumstances, be omitted. Try to record precise ages, avoiding estimated ages. For example: if a man claims to be "about 40", explain him that it is necessary to find out the exact number of years. If the person does not remember or does not know his or her age, try to help calculate it by any means; for example, if the person is a woman, ask how old she was what when her first child was born, with that information plus the age of the child the age is known.
Therefore, the enumerator can use any method in finding out the age of the enumerated person. If enumerating a stranger who, for any reason, spent the night prior to Census Day and at the time of enumeration is not present, ask to the family members the estimated age of that person.
As seen from the above comments, the enumerator should investigate, through any method, the age of all enumerated persons and make the corresponding annotation in the form.