What comes up to your mind as you read the question "Is it time?", what is it time for: asking that person out, leaving your job, etc.? Whatever it is, take the required amount of time to chose: asking someone out has no downside but leaving your job does. A good way to know is if it's the third time you're asking yourself this question, a better way to know is if your emotions outweigh a deep logical analysis, the best way to know is if you try. This question can be reframed as "How hard will you regret not trying later?". It took a few encounters for me to ask my girlfriend out but years in school system prior to knowing which career to pursue. The only right way to answer the question is to be selfish and disregard every external judgments you can think of: is it your time?