# Expression question

**URL:** <https://forum.inductiveautomation.com/t/expression-question/19846>\
**Category:** Ignition\
**Created:** [September 26, 2018, 11:45pm UTC](https://forum.inductiveautomation.com/t/expression-question/19846 "2018-09-26T23:45:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![paulm1](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paulm1/32/5900_2.png) [@paulm1](https://forum.inductiveautomation.com/u/paulm1)\
**Post date:** [September 26, 2018, 11:45pm UTC](https://forum.inductiveautomation.com/t/expression-question/19846/1 "2018-09-26T23:45:17Z")

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I am curious, In an Expression, What are the differences between -

> [@Timer SCripts](https://forum.inductiveautomation.com/t/timer-scripts/7812/5):
>
> dateFormat({[System]Client/System/CurrentDateTime},"HH:mm:ss")

and -  
`dateFormat(now(),"HH:mm:ss")`

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**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\
**Post date:** [September 27, 2018, 11:02am UTC](https://forum.inductiveautomation.com/t/expression-question/19846/2 "2018-09-27T11:02:40Z")

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In the context of that thread, nothing. but there really is a difference.

_now()_ uses the host computers clock. So if you use it in a component or client tag, the client’s clock is used. In ‘regular’ tags, the gateway’s clock is used.

_{[System]Client/System/CurrentDateTime}_, as the name implies, always points to the client’s clock.

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<div class="post-metadata">

**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [September 27, 2018, 2:51pm UTC](https://forum.inductiveautomation.com/t/expression-question/19846/3 "2018-09-27T14:51:14Z")

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There’s also a theoretical (almost nonexistent) difference in latency, because now() will directly call out and create a new Java Date instance, where the tag read has to dispatch through a few more layers. In practice, I doubt it would make even a few milliseconds difference.