As with the day, you should never need to write out the year when writing the date in Spanish. Knowing how to write out the year will allow you to say the date correctly in your mind, though, and may also make it easier to pronounce the date when you need to say it out loud.
The light reactions of photosynthesis produce ATP, which provides the Calvin cycle with the necessary energy. In addition, the NADPH produced by the light reactions provides the reducing power to put glucose together.
During photosynthesis, light energy has been converted into chemical energy stored in ATP and NADPH. The light-independent Calvin cycle uses the energy from these short-lived energy carriers to convert carbon dioxide into organic compounds that can be used by the organism.