first time—said of the very first occasion of smth. (similar events could possibly follow later though not necessarily):
- She put on her hat and shawl and, realizing it was the first time she was to leave him at home, she hugged and kissed him.
Note: The expression is not equivalent in meaning to the phrase first time round—(also: first time around) used of the first instance of some cyclic or repeated event:
- John didn’t pass the bar exam the first time round. He passed it on his second try.
for the first time—as the first instance since some past point in time:
- Negotiations began in the 1950s when it became clear for the first time that coastal resources needed protection.