machine/rp5c15.cpp: implement set_year_offset setter, fix x68k default year setup to be current rather than -20

src/devices/machine/ds1386.h

@@ -166,8 +166,6 @@ class ds1386_device : public device_t,
 	void safe_intb_cb(int state);
 	void safe_sqw_cb(int state);
 
-	void set_current_time();
-
 	void check_tod_alarm();
 	void time_of_day_alarm();
 	void watchdog_alarm();

src/devices/machine/rp5c15.cpp

@@ -109,6 +109,14 @@ enum
 DEFINE_DEVICE_TYPE(RP5C15, rp5c15_device, "rp5c15", "Ricoh RP5C15 RTC")
 
 
+// x68k wants an epoch base (1980-2079) on init, mz2500 do not ("print date$" under basicv2)
+// megast_* tbd
+void rp5c15_device::set_current_time(const system_time &systime)
+{
+	const system_time::full_time &time = m_use_utc ? systime.utc_time : systime.local_time;
+	set_time(true, time.year + m_year_offset, time.month + 1, time.mday, time.weekday + 1,
+		time.hour, time.minute, time.second);
+}
 
 //**************************************************************************
 //  INLINE HELPERS

src/devices/machine/rp5c15.h

@@ -34,10 +34,13 @@ class rp5c15_device :   public device_t,
 
 	auto alarm() { return m_out_alarm_cb.bind(); }
 	auto clkout() { return m_out_clkout_cb.bind(); }
+	void set_year_offset(int year) { m_year_offset = year; }
 
 	uint8_t read(offs_t offset);
 	void write(offs_t offset, uint8_t data);
 
+	virtual void set_current_time(const system_time &systime) override;
+
 protected:
 	// device-level overrides
 	virtual void device_start() override;
@@ -70,6 +73,8 @@ class rp5c15_device :   public device_t,
 	int m_16hz;                 // 16 Hz condition
 	int m_clkout;               // clock output
 
+	int m_year_offset = 0;
+
 	// timers
 	emu_timer *m_clock_timer;
 	emu_timer *m_16hz_timer;

src/emu/dirtc.h

@@ -51,7 +51,7 @@ class device_rtc_interface : public device_interface
 	void set_use_utc(bool use_utc) { m_use_utc = use_utc; }
 
 	void set_time(bool update, int year, int month, int day, int day_of_week, int hour, int minute, int second);
-	void set_current_time(const system_time &systime);
+	virtual void set_current_time(const system_time &systime);
 
 	bool has_battery() const { return rtc_battery_backed(); }
 

src/mame/sharp/x68k.cpp

@@ -1282,6 +1282,7 @@ void x68k_state::x68000_base(machine_config &config)
 
 	RP5C15(config, m_rtc, 32.768_kHz_XTAL);
 	m_rtc->alarm().set(m_mfpdev, FUNC(mc68901_device::i0_w));
+	m_rtc->set_year_offset(20);
 
 	/* video hardware */
 	SCREEN(config, m_screen, SCREEN_TYPE_RASTER);