What do you think is the total time saved on debugging, Google-searching, testing, etc..., by all of the developers of the world collectively as a result of Stack Overflow providing quick, reliable answers to their issues?
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Jon Skeet can give you the precise answer.
The company has offered a number for the amount of times a developer got help, in the about page it currently says:
Times a developer got help
So if you consider each of those times 1 minute it would give roughly 96.270 years.
The number itself has been discussed on Meta Stack Overflow, see "46.8+ Billion Times a developer got help" - how is this calculated?