Difference between to and until? [duplicate]
It's ambiguous.
Some may read it as including April 2013, others may not. I'd probably read it as inclusive.
American English uses the inclusive word through:
- I worked at company X from April 2012 through April 2013.
For unambiguous British English, add extra wording:
I worked at company X from April 2012 to April 2013, inclusive.
I worked at company X from April 2012 through to April 2013.
I worked at company X from April 2012 up to and including April 2013.