Question 1

How to parse a date string with a timezone using qdate?

Accepted Answer

qdate can parse date strings with timezones automatically if included, like '2013-12-31 08:15pm PST'. Use functions like to_date/1 or to_date/2 with the string, and qdate will extract the timezone and convert as needed. For custom formats, register a parser with qdate:register_parser/2.

Question 2

What's the difference between qdate and ec_date for Erlang date handling?

Accepted Answer

qdate builds on ec_date by adding timezone support from erlang_localtime, along with features like deterministic parsing, custom parsers, and date arithmetic. While ec_date only handles formatting and parsing without timezones, qdate provides a unified interface for timezone-aware operations.

Question 3

How to handle ambiguous times during daylight saving time changes in qdate?

Accepted Answer

qdate offers disambiguation options with parameters like prefer_standard, prefer_daylight, or both. When converting dates, you can specify how to handle ambiguities, as shown in the examples with to_date/3 and disambiguation arguments.

Question 4

Can I use ISO 8601 date formats with qdate?

Accepted Answer

qdate primarily uses PHP-style format strings, but you can register custom parsers for ISO 8601 or other formats. The library includes an optional relative time parser, and you can extend it to support additional date representations.

Question 5

How to install and configure qdate in an Erlang project?

Accepted Answer

Add qdate as a dependency in your rebar.config or mix.exs, and ensure erlang_localtime and ec_date are available. Configure deterministic parsing and default timezone via application environment variables, as described in the 'Configuration Sample' section.

Question 6

What are the performance implications of using qdate for high-frequency date operations?

Accepted Answer

qdate adds abstraction layers for format conversion and timezone management, which might introduce overhead. For critical performance paths, consider caching conversions or using direct Erlang functions where possible, but qdate is optimized with functions like sort/3 for efficiency.

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