Grandma told her grandchildren: "Today I am 60 years and 50 months and 40 weeks and 30 days old."

When was the last birthday Grandma had?

(L. Hozová)

Hint. How many whole years are 50 months?
50 months are four years and 2 months. Thus, the grandmother was at least 64 years old. The remaining 2 months, 40 weeks, and 30 days represent roughly one additional year. We need to accurately determine whether it is more or less, so we will convert the given data into days.

2 months can have 59 days (January and February, or February and March in a non-leap year), 60 days (January and February, or February and March in a leap year), 61 days (almost all other pairs of months), or 62 days (July and August, or December and January). 40 weeks and 30 days is $40 \cdot 7 + 30 = 310$ days.

In total, 2 months, 40 weeks, and 30 days represent at least 369 and at most 372 days. This is always more than a year (and less than two). The grandmother had her last 65th birthday.