本篇文档介绍 Wilddog Sync 的高级特性，用于实现更丰富的场景需求。
[WDGServerValue timestamp] 用于记录当前 云端时间戳。
例如，在servertimestamp 节点下记录当前云端时间：
Objective-C
Swift
```objectivec
WDGSyncReference *currentServerTimeRef = [[WDGSync sync] referenceFromURL:@"https://samplechat.wilddogio.com/servertimestamp"];
//写入当前云端时间戳
[currentServerTimeRef setValue:[WDGServerValue timestamp]];
```
```swift
let currentServerTimeRef = WDGSync.sync().reference(fromURL: "https://samplechat.wilddogio.com/servertimestamp")
//写入当前云端时间戳
currentServerTimeRef.setValue(WDGServerValue.timestamp())
```
/.info/serverTimeOffset 节点用于记录本地时间和云端时间的差值。监听该节点可以获取时钟偏差。
例如，利用时钟偏差可以计算云端时间：
Objective-C
Swift
```objectivec
WDGSyncReference *offsetRef = [[WDGSync sync] referenceWithPath:@".info/serverTimeOffset"];
[offsetRef observeEventType:WDGDataEventTypeValue withBlock:^(WDGDataSnapshot *snapshot) {
offset = [(NSNumber *)snapshot.value doubleValue];
double estimatedServerTimeMs = [[NSDate date] timeIntervalSince1970] * 1000.0 + offset;
}];
```
```swift
let offsetRef = WDGSync.sync().reference(withPath: ".info/serverTimeOffset")
offsetRef.observe(.value, with: { snapshot in
if let offset = snapshot.value as? Double {
let estimatedServerTimeMs = NSDate().timeIntervalSince1970 * 1000.0 + offset
}
})
```