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TSTooI Documentation This allows the time series to be referred to as x during further processing (e.g., when manipulated with commands). Whether full identifiers or aliases are used, the overall identifier must be unique during processing to guarantee that time series commands are processed as desired (duplicate aliases and identifiers can be present but the first one found will be used -see Section 2.3 Time Series Commands and Processing Sequence for an example). TSTooI ignores case when comparing identifiers, aliases, and other commands, although it is good practice to be consistent. When editing commands, TSTooI does not normally shown the input type and input name parts of the identifier because this information is most appropriate for read commands. There are cases where two time series identifiers will be the same except for the input type and name. In these cases, an alias should be assigned when reading the time series and the alias used in later commands. If for some reason an alias cannot be used, the input type and name may need to be manually added because the command editors do not display by default. 2.2 Date/Time Conventions TSTooI uses date/time information in several ways 1. data values in time series are associated with adate/time and the precision of all date/time information should be consistent within the time series, as discussed below, 2. the data interval indicates the time spacing between data points and is represented as a multiplier (optional if 1) and a base (e.g., Day, 24Hour), 3. the period of a time series is defined by start and end date/time values, using an appropriate precision, 4. an analysis period may be used to indicate when data processing should occur, 5. output is typically formatted for calendar year (January to December), water year (October to November), or irrigation year (November to October) -calendar year is the default but can be changed in some commands and output. A date/time has a precision. For example, 2 0 0 2- 0 2 has a monthly precision and 2 0 0 2- 0 2- O l has a daily precision. Each date/time object knows its precision and "extra" date/time information is set to reasonable defaults (e.g., hour, minute, and second for a monthly precision date/time are set to zero and the day is set to 1). The date/time precision is important because TSTooI uses the date/time objects to iterate through data, to compare dates, and to calculate a plotting position for graphs. Specifying date/time information with incorrect precision may cause inconsistent behavior. The TSTooI documentation and user interface typically use ISO 8601 International Standard formats for date/time information. For example, dates are represented using YYYY-MM-DD and times are represented using hh : mm : s s. A combined date/time is represented as YYYY-MM- DD hh : mm : s s. In order to support common use, TSTooI also attempts to handle date/time information that uses United States and other date formats. In such cases, the length of the date/time string and the position of special characters are used to make a reasonable estimate of the format. Using ambiguous formats (e.g., two-digit years that may be confused with months) may cause errors in processing. Adhering to the ISO 8601 standard formats will result in the fewest number of errors. However, it is understood that various input types use other date/time formats. Plotting positions are computed by converting dates to floating point values, where the whole number is the year, and the fraction is the fractional part of the year, considering the precision. The floating-point Introduction - 4