The way numbers are represented internally is seldom useful for human consumption. Large numbers are hard to read, currency is limited to two digits after the decimal point, and simple operations can easily result in undisplayable numbers such as 0.7000000000000001.
Formatting tools allow numbers to be displayed as strings, formatted according to a template. But culture also influences how dates and numbers are represented. Many countries use commas as decimal points, and dots as thousands separators. A date represented as 3/6/2019 may refer to March 6, 2019 or to June 3, 2019, depending on the country where you read it. The d3-format and d3-time-format modules, which are both part of the default bundle, deal with these issues with functions that format and parse dates and numbers by using string templates based on a locale.
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