Direct answer
A 4-hour forex candle forms and then closes at the end of each fixed 4-hour time interval used by your chart. During the interval, the candle is “building” (its open, high, low, and last price update). Once the interval ends, the candle “completes” and a new 4-hour candle begins.
Mechanics: what “4 hour candle” means
A “4-hour candle” is created by aggregating market prices into blocks of 4 hours. Each candle has four standard price points: open (first price in the interval), high (highest price in the interval), low (lowest price in the interval), and close (last price in the interval).
How do you determine the exact moment it forms?
- Your chart chooses a start point for each 4-hour block (often aligned to a provider’s or platform’s time grid).
- The candle updates as new price ticks or bars arrive within that 4-hour window.
- At the end of the window, the chart finalizes the candle values using the last available price for that interval.
Because the candle’s end time depends on the chart’s chosen time alignment, two platforms can sometimes show slightly different candle boundaries for the same market and timeframe.
Example checks to confirm in your own chart
You can verify the candle closing times independently:
- Note the timestamp where one 4-hour candle’s close appears on your chart, then check that the next candle starts immediately after that timestamp.
- If you compare the same pair across two platforms, look for differences in the displayed 4-hour boundaries; timezone settings and data feed timing can shift perceived candle start/end.
- During the final minute(s) of the 4-hour interval, observe how the candle’s high/low can still change until the interval ends—then those values become fixed for that candle.
Limitations and uncertainty
- This explanation is general and applies to how candles are constructed on charts; it does not guarantee the exact boundary times for every broker or platform.
- Candle boundaries can vary with timezone and the chart’s internal alignment of 4-hour intervals.
- If your data feed is delayed or aggregated differently, the “close” moment you see may not match what another platform shows.
What this means for “when do they form”
In practical terms, a 4-hour candle is formed continuously while the interval is active and becomes complete only when the chart reaches the end of that interval. To know the exact times on your screen, rely on the timestamps and candle transitions shown by your specific chart configuration rather than assumptions about a universal clock.