STM32F407 RTC读日期错误是什么原因

使用STM32F407 标准库的RTC例程，调用函数RTC_GetDate(RTC_Format_BIN, &RTC_DateStructure);读取日期，每5S读一次，发现在每天的凌晨时，小时值读出来，可以从23:59:59 正确的读到第2天的00:00:04S，而日期值在过凌晨后，还是前一天的日期，大约再读1分钟得样子，日期读出来才更新，不知道是什么原因，望各位朋友帮忙分析分析，谢谢。
The current time is :  12-12-12 23:59:56
The current time is :  12-12-12 23:59:59
The current time is :  12-12-12 00:00:04
The current time is :  12-12-12 00:00:09
The current time is :  12-12-12 00:00:14
The current time is :  12-12-12 00:00:19
The current time is :  12-12-12 00:00:24
The current time is :  12-12-12 00:00:29
The current time is :  12-12-12 00:00:34
The current time is :  12-12-12 00:00:39
The current time is :  12-12-12 00:00:44
The current time is :  12-12-12 00:00:49
The current time is :  12-12-12 00:00:54
The current time is :  12-12-12 00:00:59
The current time is :  12-12-12 00:01:04
The current time is :  12-12-12 00:01:09
The current time is :  12-12-12 00:01:14
The current time is :  12-12-12 00:01:19
The current time is :  12-12-12 00:01:24
The current time is :  12-12-13 00:01:29
The current time is :  12-12-13 00:01:34