文件的修改时间与过去的修改时间相比

Question

我的代码：

import os
from datetime import datetime
now = str(datetime.now())
with open('now.txt', 'w') as f:
    f.write(now + '\n')

print('now:', now)
print()
print('stat:')
os.system('stat now.txt')

输出示例如下：

now: 2018-10-07 06:22:52.293084

stat:
  File: now.txt
  Size: 27              Blocks: 8          IO Block: 4096   regular file
Device: 801h/2049d      Inode: 543300      Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/   susam)   Gid: ( 1000/   susam)
Access: 2018-10-07 02:58:04.219272291 +0000
Modify: 2018-10-07 06:22:52.288283252 +0000
Change: 2018-10-07 06:22:52.288283252 +0000
 Birth: -

输出和程序似乎表明文件是在2018-10-07 06:22:52.293084或之后创建的，但是根据stat输出的文件修改时间是过去的：2018-10-07 06:22:52.288283 。这怎么可能？