Synoptic Code max/mins

I've been looking at the max/mins reported in the synoptic code obs across
the world, and have discovered that the "standards" for reporting max/mins
vary widely from one country to the next. For example, the UK reports a
min at 6Z for the 12 hour period ending at 6Z. Iceland reports mins at 9z,
presumably for the 12 hours ending at 9Z. But in Canada, the min reported
at 18Z is the 24 hour min, and the max reported at 12Z is the 24 hour max
for the period 6Z to 6Z. Does anyone know of a list of the various
international standards for reporting max and mins?

Thanks,
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 Jeff Masters
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