Spreadsheets confuse non-dates with dates, and automatically interpret certain number strings with 2 colons as [h]:mm:ss. Grrr. I’ve now found another example of spreadsheets doing unexpected things with plain-text data. By default, spreadsheet programs see quotes (“) as string delimiters. If there’s a quote at the start of a data item but none at the end, the results are… interesting.

Source: LXer – Spreadsheet annoyance no. 3: quotes have priority