Daylight saving

A civil time adjustment legislated per jurisdiction, advancing the local clock in spring and returning it in autumn. Financial centres that observe it move their working day against every centre that does not, and the changeover dates are not aligned: Europe and North America change on different dates, which produces a fortnight twice a year when the usual offset between them is wrong.

The effect is a change of frame rather than a change of market. A session is stationary in its own local time and appears to move only when it is read from a clock that stayed still. Where a reader's own zone does not observe the change, as the Gulf does not, the reader's clock is the fixed one and every foreign session arrives an hour earlier or later for part of the year. Nothing about liquidity, the instruments quoted, or the behaviour of participants is implied by the shift.

Two practical consequences follow. Anything defined by a foreign clock moves with it, including the daily cut off at which the value date of open positions rolls and the timestamps a platform stamps its candles with, so a chart's session boundaries can appear to move for a fortnight. And the dates are set by legislation rather than by convention: legislatures have amended them before and several jurisdictions have abolished the practice, so a rule memorised once is checked rather than assumed.