the s&p is up %?? from what? when? how?

Alright i have tried searching for this and no matter what keywords i use all i get are articles about certain indices or stocks going up or down certain percents, my question however is , what percent and from what?
like okay , "the s&p is up .40% right now" ok .40% from yesterdays close? form yesterdays open? or from this day last year? from when? and how is this calculated because unless im doing the math wrong it does not come out to .40%
please some insight wold be appreciated :/ i know its kind of basic but i just never caught grasp of this idea

eddiea6987 said:

from yesterdays close?

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Should be this unless they say since last year or year to date, for instance.

If you're going by the tickertape or what your platform says than yes it's yesterday's close. Take how many points it moved in the given day you're looking at and divide it by the previous close.

thank you very much guys