> For the complete documentation index, see [llms.txt](https://longer-vision-robot.gitbook.io/arduino-full-stack/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://longer-vision-robot.gitbook.io/arduino-full-stack/02_programming_grammar/05_time_functions.md).

# 2.5 Time Functions

## 2.5.1 void delay(ms);

* **brief**: delay several milliseconds.
* **param**:
  * **ms**: milliseconds to delay.
* **return**: void.

## 2.5.2 void delayMicroseconds(us);

* **brief**: delay several microseconds.
* **param**:
  * **us**: microseconds to delay.
* **return**: void.

## 2.5.3 unsigned long millis();

* **brief**: return the time length in milliseconds since the most recent rebooting. Clearly, the longest time that can be recorded is 2^32-1 milliseconds. After that, the time length will starts from 0 again.
* **param**:
  * void
* **return**: unsigned long.

## 2.5.4 unsigned long micros();

* **brief**: return the time length in microseconds since the most recent rebooting. Clearly, the longest time that can be recorded is 2^32-1 microseconds. After that, the time length will starts from 0 again.
* **param**:
  * void
* **return**: unsigned long.