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It often happens that on an OPeNDAP server there is data available for multiple forecasts with different forecast times. If the time periods of the forecasts overlap, then only one of the forecasts can be imported at a time. If there is a separate file for each forecast, then this can be done by specifying the URL of the required file in the import configuration. However, when such data is imported in an operational system, then the import URL should be changed each time a new forecast becomes available on the OPeNDAP server. If the URLs for the different forecasts contain the forecast time and only differ in forecast time, then the tags TIME_ZERO and/or RELATIVE_TIME_IN_SECONDS can be used to solve this problem. The import will replace any TIME_ZERO tags in the URL with the time zero (forecast time) of the current import run. Any RELATIVE_TIME_IN_SECONDS tags in the URL will be replaced with a time that equals (time0 + relativeTime), where time0 is the time zero (forecast time) of the current import run and relativeTime (specified in the tag) is a time relative to time0 in seconds (can be negative). The time is formatted using the dateFormat that is specified in the tag. This way different forecast data is imported each time the import runs for a different time zero.
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