lede openwrt opkg update Failed

lede(openwrt)初始化安装以下，在进行软件安装时会出现：Unknown package 'xxxx'.的问题。比如在安装openssh-sftp-server会出现，Unknown package 'openssh-sftp-server'.。其实并不是软件中心没有这个包，也是我们本地维护的软件列包中没有与软件中心进行同步。
同步的命令为：opkg update，此命令可能会出现如下错误：

Downloading https://mirror.0x.sg/lede/snapshots/targets/mvebu/generic/packages/Packages.gz.
Downloading https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/base/Packages.gz.
Downloading https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/telephony/Packages.gz.
Downloading https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/packages/Packages.gz.
Downloading https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/routing/Packages.gz.
Downloading https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/luci/Packages.gz.
Collected errors:
 * opkg_download: Failed to download https://mirror.0x.sg/lede/snapshots/targets/mvebu/generic/packages/Packages.gz, wget returned 5.
 * opkg_download: Failed to download https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/base/Packages.gz, wget returned 5.
 * opkg_download: Failed to download https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/telephony/Packages.gz, wget returned 5.
 * opkg_download: Failed to download https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/packages/Packages.gz, wget returned 5.
 * opkg_download: Failed to download https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/routing/Packages.gz, wget returned 5.
 * opkg_download: Failed to download https://mirror.0x.sg/lede/snapshots/packages/arm_cortex-a9_vfpv3/luci/Packages.gz, wget returned 5.

但如果直接运行ping mirror.0x.sg发现网络是通的。通常这种原因是由于在进行https请求时签名错误引起的，而签名正确的前提是系统拥有一个正确的时间。此时则需要使用date命令来查看系统时间，系统时间不正确的话修正为正确的值后，重新执行opkg update即可。除了使用命令进行更新外，还可以在界面上如下操作：

同步后刷新页面时间便变更为当前的时间了。