Working With Time
As discussed above in the time format section, time is held as a floating point number of days. This means that if you want to find the date some number of days (say 90) from a given date, just enter the date (with the Date function), then enter + 90 and tap ENTER. If you are in the date format display, it will show the end date. All the time functions are under the Time function dropdown button.
Format of Dates in Expressions
Napier uses Visual Basic date formats which look like this:
#1/26/01 12:00:00#
for January 26, 2001, 12 Noon. The # symbols are required to separate the date from the rest of the command.
Unfortunately, the current version of VBScript which is in the PocketPC does not support non-US time/date formats, so Napier only accepts that format which is Month/Day/Year separated by the ì/î character. Hopefully Microsoft will support the full locale specific Date/Time format in the future. The information box will show dates and times in local format, but they cannot be used in commands.
Real Time ñ Now, Intrvl and Beep
These can be used to gather data, or just as general time pieces.
Now
This shows the current time, accurate to a second. If you execute it by tapping DataIn, you will get a list of the time stamps.
Intrvl
This shows the elapsed seconds since its last use, accurate to a millisecond, if that is supported on your PocketPC hardware. Note that this answer is in seconds, not the standard time representation of days. To use this value with other time functions, such as adding it to a time, first convert it with the Sec function. The displayed answers are generally more useful this way.
Intrvl can be used if you are gathering a set of elapsed times, perhaps lap times in a race, or some other repeating event. If you repeatedly execute Intrvl, it will show the time since the last one. If you use DataIn, the intervals will be appended to the Data Set, so you can do further analysis on them. Since Intrvl has no separate reset function, if you are timing events which donít start immediately after the last one, just tap ENTER for the start of the event, and DataIn for the end. The ENTER tap at the start of each event, will show the elapsed time between events, but it wonít be saved in the Data Set. However, by tapping DataIn at the event end, you both see the time since the start, and simultaneously save it in the Data Set. You donít have to do anything to initially start Intrvl running, itís always on.
In the Options, if you set the Show Timer checkbox, the running elapsed time will be shown in the information box.
Beep
This possibly annoying function acts as a metronome to provide a set number of beeps at regular intervals. If you are gathering 50 observations every 20 seconds, set Beep to beep every 20 seconds for 50 times, and when you are ready to start, tap Enter. Then, each time it beeps, enter the observed value and tap DataIn. To stop it early, just enter 0 for a count and execute it.
In the Options, if you set the Show Timer checkbox, the running elapsed time will be shown in the information box.
Date Function
This is the Date function display:
To add 90 days to this date, the command bar will look like this:
Tapping the ENTER key will generate this:
DHMS Function (Days, Hours, Minutes, Secs)
You can do this with fractional days also, if you use the DHMS function (Days, Hours, Minutes, Secs), you can do things like #1/1/01 12:00:00# + DHMS(90, 3, 36, 5), that is adding 90 days, 3 hours, 36 minutes, 5 seconds to noon, Jan 1, 2001, which would give you:
Remember that internally, all times are stored as doubles representing days, so the above DHMS(90, 3, 36, 5) internally is kept as 90.1500579. I mention this, because you may be doing some set of calculations that results in a day count that you then need to add to a date. Just do it directly. As long as you have days, you donít need to do any conversions to add it to a date.
Day, Hr, Min, Sec Functions
These are all used to convert time in their units to days. If you do a series of calculations that give you a time interval in seconds, and you need to add that to a date, just use that as the argument to the Sec function to get the days value you need for the addition. Day, Hr and Min are similar, although Day is really there just for decoration, since directly adding a number is the same thing.
Subtracting Dates
Since dates are just day counts, if you subtract one date from another, it will give you the number of days between them.
Date Display formats
There are several date display formats in the display format dropdown in the Options dialog (tap Options button to show it). These all generate answer displays that are actually functions that when executed give a standard time value, the number of days. For example if the display format is Hours, it will show something like
Hrs(8)_
If you were to switch to normal number display format it will show:
0.3333_
because 8 hours is 1/3 of a day. Minutes and seconds are handled similarly.
When you are in one of the time formats, the information box will display a more readable version of the answer. If it is showing a date, the information box dropdown will show the day of week, date, and time.
The Gen Time display format option switches between the different time formats depending on the size of the answer to attempt to provide the most useful display format.
Accessing Dates from VBScript
If you are loading your own VBScript programs (discussed more below), you can use the dates generated by Napier, because VBScript also uses doubles in the same way to store dates.