jinzhu/now is a lightweight, zero-dependency Go library for time manipulation. It provides comprehensive functions to compute the beginning and end of various time units (minute, hour, day, week, month, quarter, year, half-year), parse flexible date/time strings into Go `time.Time` values, and handle configurable week start days (e.g., Monday vs Sunday) and time zones. The core pattern is a `Now` struct wrapping `time.Time` with a `Config` for customization, enabling fluent calls like `now.With(t).BeginningOfMonth()`. The library is widely used (4.7k stars) and thoroughly tested, with careful DST handling and a clever partial-date parser that merges string components with contextual current time. It is a pure library without external dependencies, targeting Go 1.12+ and suitable for any Go project needing robust time calculations or flexible date parsing.