Which of the following statements is more common and why?
- I became 20 yesterday.
- I turned 20 yesterday.
"Became" would be understood, but "turned" is the normally used verb, at least in the US. "Was" does not suit this context; it would more likely be used to reference the distant past; i.e., I was 20 when the Beatles arrived in America.
In my opinion turn would be an appropriate choice. Both may be used to denote changes. However, turn is used when a the process is still in continuation and gradual per se, like aging, while become is used when the phrase is more definitive and result oriented. For example:
- What do I have to do to become a pilot?
- He turned 100 years old yesterday.