You want to know the number of days left until December 18, 2015. In order to answer that question, you need to know how many weeks, days, and hours there are between December 18 and your current date. As we all know, 91 days equal 13 weeks, which means that you have 191 days until your special day. The difference between the start and end dates is a matter of choice, but 92 days means that you have seven months in 2015.
If you’re wondering how many days until December 18, you need to know that it’s a Friday, and the year has exactly fifty-one weeks and thirty-six days. That’s a long time for a date to pass, so let’s start by calculating the number of weeks and days between December 18 and your current date. This is because December 18th falls in week fifty of the year. Therefore, the remaining days are based on this fact. And because 2015 is not a leap year, this doesn’t mean that you have thirty-one weeks, but rather 365.