当日
とうじつ · toujitsu · JLPT N2 · noun
day
📅 当 (that very, on-the-spot) + 日 (day) = the very day that was set
当 means 'that very' or 'hitting the target', and 日 is 'day'. Together they name the day something was appointed, or the same day it happens.
当 — small ⺌ + crown 冖 + hand 彐 (simplified from 當: 尚 + 田)
Originally written 當, combining 田 'field' with 尚 as a phonetic. The early sense was 'to match' or 'face' a field of equal value, extended to 'correspond to', 'ought to', and 'serve as'. The simplified form 当 streamlines the upper 尚 component.
日 — pictograph of the sun
日 is a pictograph of the sun, originally drawn as a circle with a dot or stroke inside representing the sun's substance. Over time the round shape was squared off into the modern rectangular form. It means 'sun' and by extension 'day'.