How can I detect the first candle of the day in Pine Script?

Yes sir, you can detect the first candle of a new day by comparing the current bar’s day with the previous bar’s day.

A simple way is to use dayofmonth:

//@version=6
indicator("First Candle of Day", overlay=true)

newDay = ta.change(dayofmonth) != 0

plotshape(
     newDay,
     title="First Candle",
     style=shape.labelup,
     location=location.belowbar,
     text="Day Start"
)

Here, ta.change(dayofmonth) checks whether the day has changed compared with the previous candle.

When the day changes:

-> newDay becomes true

-> The current candle is treated as the first candle of the new day

-> Your required logic can be executed only when newDay is true

For example:

if newDay
    // Your logic here

You can use this for tasks such as:

-Resetting daily variables

-Capturing the first candle’s high and low

-Calculating daily opening levels

-Starting a new daily trading cycle

-Resetting strategy conditions

So the main idea is to detect the change from the previous day’s value rather than checking every candle individually.