Time tag word line shift to reduce failed bit count spikes for edge word lines

A method, comprising:

• sequentially programming a first plurality of word lines of a block of NAND memory, the first plurality of word lines being less than all of the word lines of the block;
• recording a word line number of last programmed of the sequentially programmed word lines;
• and
• concurrently with programing the first plurality of word lines of the block, writing a time tag value to one of the first plurality of word lines of the block by:
• determining whether the word line number of last programmed of the sequentially programmed word lines is one of one or more predetermined word lines;
• in response to the last programmed of the sequentially programmed word lines not being one of the one or more predetermined word lines, writing the time tag value to one of the predetermined word lines;
• and
• in response to the last programmed of the sequentially programmed word lines being one of the one or more predetermined word lines, writing the time tag value to a word line of the block of NAND memory other than one of the predetermined word lines.

A non-volatile memory system, comprising:

• a memory array comprising a plurality of blocks of non-volatile memory cells connected along word lines;
• and
• one or more control circuits connected to the one or more of memory arrays, the one or more control circuits configured to:
• sequentially program a first plurality of word lines of a first block of the memory array, the first plurality of word lines being less than all of the word lines of the block and ending with a last written word line;
• write time tag values to a plurality of the first plurality of word lines, including a first predetermined word line;
• and
• read a first one of the time tag values, where to read the first time tag value the one or more control circuits are configured to:
• determine whether the first predetermined word line is the last written word line;
• if the first predetermined word line is not the last written word line, read the first time tag value from the first predetermined word line;
• and
• if the first predetermined word line is the last written word line, read the first time tag value from a word line other than the first predetermined word line.