system-time

获取各种格式和时区的准确系统时间。当用户需要知道当前时间、日期、时间戳或想要在时区之间进行转换时使用。支持 ISO 8601、Unix 时间戳、人类可读格式和时区转换。

## 概述（中文）

获取各种格式和时区的准确系统时间。当用户需要知道当前时间、日期、时间戳或想要在时区之间进行转换时使用。支持 ISO 8601、Unix 时间戳、人类可读格式和时区转换。

## 原文

# System Time

Get accurate system time information in multiple formats.

## Quick Usage

### Current Time (Local)
```bash
date                                    # Human readable
date -Iseconds                          # ISO 8601 with seconds
date +%s                                # Unix timestamp
```

### Current Time (UTC)
```bash
date -u                                 # UTC human readable
date -u -Iseconds                       # UTC ISO 8601
date -u +%s                             # UTC Unix timestamp (same as local)
```

### Specific Timezone
```bash
TZ=Asia/Shanghai date                   # Shanghai time
TZ=America/New_York date                # New York time
TZ=Europe/London date                   # London time
```

## Common Formats

| Format | Command | Example Output |
|--------|---------|----------------|
| ISO 8601 | `date -Iseconds` | 2024-03-11T16:30:00+08:00 |
| Unix timestamp | `date +%s` | 1710145800 |
| RFC 2822 | `date -R` | Mon, 11 Mar 2024 16:30:00 +0800 |
| Custom | `date "+%Y-%m-%d %H:%M:%S"` | 2024-03-11 16:30:00 |

## Timezone Conversion

Convert from one timezone to another:
```bash
# Convert specific time from Shanghai to New York
TZ=America/New_York date -d "2024-03-11 16:30:00 CST"

# List available timezones
ls /usr/share/zoneinfo/
```

## Python Alternative (for scripting)

```python
from datetime import datetime, timezone

# Current UTC time
utc_now = datetime.now(timezone.utc)
print(utc_now.isoformat())

# Current local time
local_now = datetime.now()
print(local_now.isoformat())

# Unix timestamp
print(int(utc_now.timestamp()))
```

## Notes

- Unix timestamp is always UTC (timezone-independent)
- ISO 8601 format includes timezone offset
- Use `timedatectl` on Linux systems for system clock info