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                    فيديو شرح Working with date and timestamp in R language ضمن كورس لغة R شرح قناة Unboxing Big Data، الفديو رقم 20 مجانى معتمد اونلاين                
            
            
                There are three basic date and time classes: Date, POSIXct and POSIXlt
Class Date handles dates without times. 
Date and POSIXct are internally stored as number of seconds from January 1, 1970.
POSIXlt stores dates and times as a list of components: second, minute, hour, day, month, year, time zone etc.
POSIXct (calendar time) and POSIXlt (local time) represent dates and times.