Expert Advisor Programming by Andrew R. Young

EXPERT ADVISOR PROGRAMMING
Chapter 7
Working with Time and Date
Datetime Variables
Internally, the datetime variable is represented as the number of seconds elapsed since January 1,
1970. For example, June 15, 2009 at 0:00 (midnight) would be 1245024000. The advantage of
datetime format is that it makes past and future time comparisons and mathematical manipulations
very easy.
For example, if you wanted to check whether one date comes before or after another date, you
would do a simple relational operation. Let's say that StartDate is June 15, 2009 at 14:00, and
EndDate is June 16, 2009 at 5:00.
if(StartDate < EndDate) // Result is true
if(StartDate > EndDate) // Result is false
Another advantage is that you can add or subtract time from a particular date, simply by adding or
subtracting the appropriate number of seconds. If you want to add 24 hours to StartDate, simply
add the number of seconds in a day:
datetime AddDay = StartDate + 86400;
If you're planning to do a lot of mathematical manipulation with datetime variables, it might be a
good idea to declare some integer constants to represent certain units of time:
#define SEC_H1 3600
#define SEC_D1 86400
// Seconds in an hour
// Seconds in a day
The disadvantage of datetime format is that it is not very readable. You can't look at a value such as
1245024000 and automatically tell that it represents June 15, 2009 at 0:00. For this, we use
conversion functions to convert datetime to and from a more readable form.
Datetime Constants
A datetime constant is a date and time presented in the following string format: yyyy.mm.dd hh:mm.
For example, June 15, 2009 at 0:00 would be 2009.06.15 00:00. There are other acceptable
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