Monitors should be calibrated approximately every 6 months.
The following settings are best used when calibrating your monitor for outputting to photographic print:
White point: D55 (D50 is a little warm for photographic print)
Luminance (Lux): 120K
When using a calibration device it’s best to use the automatic display control if that is an option.
Always make sure you are editing in a well lit room with any automatic brightness features turned off. Dark spaces can trick your eyes into thinking your screen is brighter than it actually is.
Please remember that a computer screen will not exactly match a photograph because of the different methods of generating the colours that are viewed. Computer screens emit light whereas the dyes in photographs absorb light and the paper base reflects light which is not absorbed. Consequently, it is important to view photographs under standard lighting conditions when trying to assess whether the colours match what was expected from the screen image.