Table Of Contents
The Set Of 2D Points task supports date entry for the x-value. If you enter x-values in this format: MM/DD/YYYY hh:mm:ss.f where:
| Date Fields |
| MM | Months, a number from 1 to 12 |
| DD | Days, a number from 1 to 31 |
| YYYY | Years, a four digit number |
| hh | Hours, a number from 0 to 24 |
| mm | Minutes, a number from 0 to 60 |
| ss | Seconds, a number from 0 to 60 |
| f | Fraction of second, an integer |
then the x-value is interpreted as a Gregorian date. The MM/DD/YYYY part is mandatory while the hh:mm:ss.f is optional. Here are some date entry examples:
| Date | Explanation |
| 12/1/2010 | A valid calendar date |
| 12/1/2010 8:0:0 | A valid calendar date and time |
| 12/1/2010 8 | An invalid time, the time part must contain two colons and three numbers. |
| 12/1/99 | An invalid date, the year part must contain four decimals indicating the century. |
The following are a few issues when working with dates:
- The date is simply the x-value and must be followed by a y-value scalar in order to complete the 2D point entry.
- Only the Gregorian calendar is supported and the month must be the first number in the date.
- Data entry supports date or scalar representation for the x-value but not both at the same time. For table cell entry, if you enter a date for a x-value then all x-values are then interpreted as dates. If you enter a scalar for a x-value then all x-values are then interpreted as scalars in which case any previously entered dates are shown as seconds since 1/1/1970.
- If you paste in a series of dates then each date y-value entry must be on one line only, i.e.: a delimiter of a return character must separate each 2D point. In this case, date entry is determined by looking for a slash (/) in the first 20 characters of the pasteboard string. If a slash is found then all subsequent x-values are assumed to be in date format.
- In order to appear on all the coordinate systems, the date is remapped to a second since 1/1/1970 as an intrinsic basis, hence dates can also be entered as seconds since January 1, 1970.
- Dates are most important for the Curve > Date graph where the x-axis is shown in Gregorian calendar format and scaled to any of the fields specified in the table above. For example, if your x-values span months then the x-axis will show increments in months, if your x-values span years then the x-axis will span years, if your x-values span seconds then the x-axis will span seconds, and so on and so on. This autoscale feature and the resulting x-axis label format is rather complex and can be altered with the use of Skins. Also note that the x-axis tick increments are uniform in date field, but not uniform in the second basis hence the ticks may appear non-uniformly spaced. A good date graph is particularly complex.