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PHP’s date_sunset function returns a UTC timestamp. If your server’s timezone differs from the actual timezone, it may lead to inaccurate displayed times. Therefore, the first step is to ensure the correct timezone is set before calling date_sunset.
<span><span><span class="hljs-title function_ invoke__">date_default_timezone_set</span></span><span>(</span><span><span class="hljs-string">'Asia/Shanghai'</span></span><span>); </span><span><span class="hljs-comment">// Set timezone to Shanghai</span></span><span>
</span></span>This ensures that all subsequent time calculations are based on the correct timezone.
Since date_sunset returns a UTC timestamp, if your location is in a non-UTC timezone, you need to manually adjust the offset. For example, Beijing time is 8 hours ahead of UTC, which can be adjusted with simple addition:
<span><span><span class="hljs-variable">$sunsetTimestamp</span></span><span> = </span><span><span class="hljs-title function_ invoke__">date_sunset</span></span><span>(</span><span><span class="hljs-title function_ invoke__">time</span></span><span>(), SUNFUNCS_RET_TIMESTAMP, </span><span><span class="hljs-number">39.9042</span></span><span>, </span><span><span class="hljs-number">116.4074</span></span><span>); </span><span><span class="hljs-comment">// Beijing coordinates</span></span><span>
</span><span><span class="hljs-variable">$localSunset</span></span><span> = </span><span><span class="hljs-variable">$sunsetTimestamp</span></span><span> + (</span><span><span class="hljs-number">8</span></span><span> * </span><span><span class="hljs-number">3600</span></span><span>); </span><span><span class="hljs-comment">// Adjusted to Beijing time</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Beijing sunset time: "</span></span><span> . </span><span><span class="hljs-title function_ invoke__">date</span></span><span>(</span><span><span class="hljs-string">"Y-m-d H:i:s"</span></span><span>, </span><span><span class="hljs-variable">$localSunset</span></span><span>);
</span></span>Daylight saving time (DST) is a common factor that affects time calculations. In some regions, DST advances local time by one hour. If your application needs to support DST, PHP’s built-in DateTime class can handle it automatically.
<span><span><span class="hljs-variable">$datetime</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title class_">DateTime</span></span><span>();
</span><span><span class="hljs-variable">$datetime</span></span><span>-></span><span><span class="hljs-title function_ invoke__">setTimestamp</span></span><span>(</span><span><span class="hljs-variable">$sunsetTimestamp</span></span><span>);
</span><span><span class="hljs-variable">$datetime</span></span><span>-></span><span><span class="hljs-title function_ invoke__">setTimezone</span></span>(</span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title class_">DateTimeZone</span></span><span>(</span><span><span class="hljs-string">'Asia/Shanghai'</span></span><span>)); </span><span><span class="hljs-comment">// Automatically consider DST</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Adjusted sunset time: "</span></span><span> . </span><span><span class="hljs-variable">$datetime</span></span>-><span><span class="hljs-title function_ invoke__">format</span></span>(</span><span><span class="hljs-string">'Y-m-d H:i:s'</span></span>);
</span></span>This allows PHP to automatically adjust for DST based on timezone rules.
Sometimes you may not need a timestamp but prefer a formatted time string directly. In this case, you can use the SUNFUNCS_RET_STRING parameter of date_sunset, which returns a formatted time string. For example:
<span><span><span class="hljs-variable">$sunsetTime</span></span><span> = </span><span><span class="hljs-title function_ invoke__">date_sunset</span></span><span>(</span><span><span class="hljs-title function_ invoke__">time</span></span><span>(), SUNFUNCS_RET_STRING, </span><span><span class="hljs-number">39.9042</span></span><span>, </span><span><span class="hljs-number">116.4074</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Sunset time: "</span></span><span> . </span><span><span class="hljs-variable">$sunsetTime</span></span><span>
</span></span>The returned time is already in the local timezone (ensure the timezone is set correctly), eliminating the need for further timestamp adjustments.
If you are unsure of the server’s current timezone, you can use date_default_timezone_get to retrieve it and adjust the time accordingly.
<span><span><span class="hljs-variable">$currentTimezone</span></span><span> = </span><span><span class="hljs-title function_ invoke__">date_default_timezone_get</span></span><span>();
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Current timezone: "</span></span><span> . </span><span><span class="hljs-variable">$currentTimezone</span></span><span>
</span></span>This allows you to dynamically get the current timezone and make appropriate adjustments.
In some cases, the time returned by date_sunset may still have minor discrepancies. These are usually influenced by weather, geography, and other factors and cannot be completely eliminated by code. If you know the specific offset (e.g., from observational records), you can manually adjust the returned timestamp:
<span><span><span class="hljs-variable">$sunsetAdjusted</span></span><span> = </span><span><span class="hljs-variable">$sunsetTimestamp</span></span><span> + </span><span><span class="hljs-number">600</span></span><span>; </span><span><span class="hljs-comment">// Adjust by 10 minutes</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Adjusted sunset time: "</span></span><span> . </span><span><span class="hljs-title function_ invoke__">date</span></span><span>(</span><span><span class="hljs-string">"Y-m-d H:i:s"</span></span><span>, </span><span><span class="hljs-variable">$sunsetAdjusted</span></span><span>);
</span></span>When handling the timestamp returned by date_sunset, it is necessary to consider multiple factors such as timezone, daylight saving time, and geographical location. By applying the methods above, we can ensure the returned time aligns more closely with the actual time. In practice, combining the DateTime class, timezone settings, and DST rules allows for more precise timestamp adjustments to meet the needs of different scenarios.
