Money has time value mainly because of the inflation (increase in the price levels). For example, the prices of goods and services will not be same after few years when compared to previous years, hence you can't buy the same goods and services with same money after some time. This is due to time value of money. The point here is that the money today is worth more when compared to future. Hence, you need interest to the money in the future if you are foregoing the present consumption to level that inflation. Hence, time value of money is very important concept.