Create cheatsheet.md

docs/cheatsheet.md

@@ -0,0 +1,134 @@
+
+
+# Naming (compared to java.time)
+
+LocalDate => `date`
+
+LocalDateTime => `date-time`
+
+java.util.Date => `inst` 
+
+js/Date => `inst`
+
+otherwise the same as java.time
+
+# Dates and Times
+
+## Construction
+
+### Now 
+
+```clojure
+(t/date), (t/zoned-date-time), (t/instant)
+```
+
+temporarily change what clock is used to get the `now` or `where` information with `with-clock`
+
+```clojure
+(t/with-clock (t/instant "2023-08-23T15:49:21.941342Z") 
+   (t/date))
+```
+
+### Extraction 
+
+for example, get the date part out of a zdt
+
+```clojure
+(t/date (t/zoned-date-time))
+```
+
+set hours and smaller to zero
+```clojure
+(t/truncate (t/instant) :hours) 
+```
+
+### Combining parts
+
+```clojure
+(-> (t/date)
+    (t/at "00:00")
+    (t/in "UTC"))
+
+(-> (t/time "10:10")
+    (t/on (t/date)))
+```
+
+### from/to Strings 
+
+```clojure
+(t/parse-... "xxx", (t/formatter "pattern"))
+
+(t/format (t/date) (t/formatter "pattern"))
+```
+
+### from numbers 
+
+```clojure
+(t/new-date 2020 2 2) 
+(t/new-... )
+```
+round-trip to/from epoch millis
+```clojure
+(-> (t/instant) (cljc.java-time.instant/to-epoch-milli) (t/instant))
+```
+
+### Relative 
+
+```clojure
+ (t/>> (t/instant) (t/of-hours 2))
+ (t/<< ...)
+```
+
+# Amounts of Time
+
+## Construction
+
+```clojure
+(t/of-hours 24) => Duration
+(t/of-days 1) => Period
+(t/of-..)
+```
+
+### From points in time
+
+```clojure
+(t/between point-a point-b)
+```
+
+## Arithmetic
+
+```clojure
+(t/+ (t/of-minutes 5) (t/of-minutes 5) (t/of-minutes 5))
+(t/- ...)
+```
+
+## Extract parts
+
+```clojure
+(t/millis ...)
+(t/days ...)
+```
+
+# Comparison
+
+```clojure
+t/<, t/<=, t/=, ...
+t/max, t/max-by, t/min, t/min-by
+```
+
+# Predicates 
+
+```clojure
+(t/date-time? x)
+```
+
+# Units
+
+```clojure
+t/APRIL,
+t/DECEMBER ...
+
+t/FRIDAY, t/MONDAY...
+```
+
+