v5.0.0 🚨 -breaking

• 🚨 all methods now immutable by default.🚨
  -- existing code will now need to be s = s.add(1,'day')
  --- (instead of s.add(1,'day'))
• move unix-formating out of .format() into .unixFmt()
• support new {hour} oclock-style format templates
• change default .format() response to yyyy-mm-dd
• uppercase month and day names in .dayName()
• support city-names, EST, PDT, etc as input
• set default silent: true to avoid unwanted logging

5.1.0

• titlecase short-forms of months, days in .format()

v4.0.0

• format(iso) now uses . for millisecond separator: 2016-11-04T09:00:59.122Z
• adds .since() method to calculate a human-readable diff
• support string/number input to .diff()
• support ordinal inputs, like June 5th 2018
• isAwake() method
• alias for .plus() .minus() methods
• .diff() without a unit does a couple units together
• update zonefile to proper dst-flip time

v4.0.1

• support .from() and .fromNow() methods

v4.1.0

• fix 'February 30th' regression
• remove denormalized .valid boolean on Spacetime class

v4.2.0

• fix dayOfYear regression on 31st days
• support space in ISO-186 format
• update deps, use babel-env

v4.2.2

• adds .extend() method for authoring plugins

v4.3.0

• assume current year with input spacetime('July 5th')
• do larger .diff() operations (gt 1yr) in fast-mode
• support BC formatting of input and in s.format('year')
• bug fix for iso-format hour-offsets (#58)

v4.4.0

• big - swap interpretation of ISO date offsets -0500 → +5 offset #61

v4.5.0

• update a few TZ offsets in mostly eastern-Russia
• updates to 2019 Palestinian dst dates
• fixes for missing immutable setter methods

dramatic speedup

before 20k dates:   3.3s
after 20k dates:    0.8s

• fallback to UTC, instead of PST if no Intl is present
• support passing-in offsets as ISO_8601 date-strings
• add epoch-seconds warning msg
• allow getting/setting new timezones