doc.sublime-snippet文件内容：

<snippet>
  <content><![CDATA[
// ${1:说明解释} marked by yangshuiping $DATE
]]></content>
  <!-- Optional: Set a tabTrigger to define how to trigger the snippet -->
  <tabTrigger>doc</tabTrigger>
  <!-- Optional: Set a scope to limit where the snippet will trigger -->
  <!-- <scope>source.python</scope> -->
</snippet>

在User目录建一个python文件，文件名随意，内容如下：

import sublime, sublime_plugin, time

class InsertDatetimeCommand(sublime_plugin.TextCommand):
    def run(self, edit):
        date = time.strftime("<%Y-%m-%d %H:%M:%S>")
        self.view.run_command("insert_snippet", {
            "name": "Packages/User/doc.sublime-snippet",
            "DATE": date
            })

放在和快捷键同目录的地方：

D:\Program Files\SublimeText3\Data\Packages\User

设置key-binding:

{ "keys": ["ctrl+f5"], "command": "insert_datetime"}

就是这么简单就完成了，不需要额外安装包。更强大的功能可以安装InsertDate这个包。