From Dashboard settings, click the Timepicker tab. From here you can specify the relative and auto refresh intervals. The Timepicker tab settings are saved on a per Dashboard basis. Entries are comma separated and accept a number followed by one of the following units: s (seconds), m (minutes), h (hours), d (days), w (weeks), M (months), y (years).
In Grafana 2.0, it's now possible for individual Panels to override the Dashboard time picker. Please check out the [whats new in 2.0 guide](../guides/whats-new-in-v2/) for further information