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Ask HN: How do you “visualize” timezone offsets in your head?

3 points by glaberficken ↗ HN
I have always wondered how other people "visualize" this in their own heads =) when they need to do a quick mental timezone conversion.

For me it works like this: I visualize a world map sort of focused on the regions I'm converting between.

I'm based in Western Europe so lets say I'm converting between US Pacific Time and GMT and I know that for most of the year the time difference is 8 hours.

The image that would pop into my head is of a world map centered on the Atlantic ocean where I imagine the Sun going over from right to left as the day progresses, this gives me the queue that as the sun sets/"leaves" Europe it will be "arriving" over the US thus imparting the info that it is 8 hours later in GMT than PST.

Whenever i need to do a new conversion between different regions I usually always visualize it this way...I've always found it odd because a lot of friends tell me they just memorize if its Region A is X hours ahead/behind of Region B and that's it! whereas for me that doesn't seem to work.

Would love to hear your thoughts =)

7 comments

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informatimago
Yes, I usually find it easier to memorize things starting from base concepts. (I don't see the Sun moving right to left, but the Earth turning counter clockwise when seen from the North pole).

There's no way to memorize the X hours ahead/behind meaningfully, since the sign of numerical timezone offset may be flipped, depending on the operation AND on the system used. Eg. systems designed in the USA often use an opposite offset, (so they have negative offsets to Europe).

The Greenwich Observatory defines positive offsets East and negative West: http://wwp.greenwichmeantime.com/info/timezone.htm So GMT+8 is in China.

But for POSIX, GMT+8 is the USA, like in Common Lisp, where: "Time zone values increase with motion to the west, so Massachusetts, U.S.A. is in time zone 5, California, U.S.A. is time zone 8, and Moscow, Russia is time zone -3." To be noted that both those systems were designed in the USA.

glaberficken
>"(I don't see the Sun moving right to left, but the Earth turning counter clockwise when seen from the North pole)"

ha! that's brilliant! thanks for sharing

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zhte415
Working with teams around the world, I don't visualise the globe, but what they're eating.

I'm eating dinner, so US East Coast is eating breakfast, and we can have a call soon. For Mid West / West Coast, add 2-3 hours.

I'm having lunch, India is having breakfast.

I'm going to have dinner soon, Europe is going to have lunch soon.

Not that scientific, but a way to visualise what people are doing, and therefore if they're reading their email or able to answer the telephone at the time. And it's a good image for some smalltalk.

Pyrodogg
I used to visualize the sun more easily (naively) when figuring time differences. After moving from 45N to rough 60N it's gotten weirder with the even longer summer days.

The sun doesn't just "go west' as if the earth's axis had no tilt. I think that most people don't really pay attention to the path the sun makes across the sky as the year progresses. It's harder to visualize "in what position would the sun be 8 timezones away" when you account for the tilt.

It's nearing 8pm local time here in Helsinki and the sun is still quite high in the sky. Back in US central where I have family, it's nearing 12 noon. The sunlight overlaps a good deal in the summer time. In the middle of winter, we will never see the sun at the same time.

gusmd
I'm used to just thinking about GMT. I know that the UK is around GMT 0, the US is negative, and Japan is positive, so those are my starting points for other locations.

I believe it has helped me that I have lived in different time zones, so it has become second-nature.