kubernetes/vendor/google.golang.org/grpc/internal/grpcutil/encode_duration.go

const maxTimeoutValue …

// div does integer division and round-up the result. Note that this is
// equivalent to (d+r-1)/r but has less chance to overflow.
func div(d, r time.Duration) int64 { … }

// EncodeDuration encodes the duration to the format grpc-timeout header
// accepts.
//
// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests
func EncodeDuration(t time.Duration) string { … }